Merge branch 'master' into master

2018-09-27 23:40:00 +08:00 · 2018-09-27 23:40:00 +08:00 · 204139739a
parent 250946568c 3e004d900b
commit 204139739a
41 changed files with 1772 additions and 416 deletions
--- a/.github/ISSUE_TEMPLATE/bug_report.md
+++ b/.github/ISSUE_TEMPLATE/bug_report.md
@ -1,3 +1,9 @@
+---
+name: Bug report
+about: Create a report to help us improve
+
+---
+
 <!--
 If you are reporting a new issue, make sure that we do not have any duplicates
 already open. You can ensure this by searching the issue list for this
--- a/.github/ISSUE_TEMPLATE/feature_request.md
+++ b/.github/ISSUE_TEMPLATE/feature_request.md
@ -0,0 +1,44 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+
+---
+
+<!--
+If you are reporting a new issue, make sure that we do not have any duplicates
+already open. You can ensure this by searching the issue list for this
+repository. If there is a duplicate, please close your issue and add a comment
+to the existing issue instead.
+
+Use the commands below to provide key information from your environment:
+You do NOT have to include this information if this is a FEATURE REQUEST
+-->
+
+**Description**
+
+<!--
+Briefly describe the problem you are having in a few paragraphs.
+-->
+
+**Steps to reproduce the issue:**
+1.
+2.
+3.
+
+**Describe the results you received:**
+
+**Describe the results you expected:**
+
+**Output of `go version`:**
+
+```text
+(paste your output here)
+```
+
+**Excelize version or commit ID:**
+
+```text
+(paste here)
+```
+
+**Environment details (OS, Microsoft Excel™ version, physical, etc.):**
--- a/.travis.yml
+++ b/.travis.yml
@ -6,6 +6,17 @@ install:
 go:
  - 1.8.x
  - 1.9.x
+  - 1.10.x
+  - 1.11.x
+
+os:
+  - linux
+  - osx
+
+env:
+  matrix:
+    - GOARCH=amd64
+    - GOARCH=386

 script:
  - go vet ./...
--- a/PULL_REQUEST_TEMPLATE.md
+++ b/PULL_REQUEST_TEMPLATE.md
@ -0,0 +1,45 @@
+# PR Details
+
+<!--- Provide a general summary of your changes in the Title above -->
+
+## Description
+
+<!--- Describe your changes in detail -->
+
+## Related Issue
+
+<!--- This project only accepts pull requests related to open issues -->
+<!--- If suggesting a new feature or change, please discuss it in an issue first -->
+<!--- If fixing a bug, there should be an issue describing it with steps to reproduce -->
+<!--- Please link to the issue here: -->
+
+## Motivation and Context
+
+<!--- Why is this change required? What problem does it solve? -->
+
+## How Has This Been Tested
+
+<!--- Please describe in detail how you tested your changes. -->
+<!--- Include details of your testing environment, and the tests you ran to -->
+<!--- see how your change affects other areas of the code, etc. -->
+
+## Types of changes
+
+<!--- What types of changes does your code introduce? Put an `x` in all the boxes that apply: -->
+
+- [ ] Docs change / refactoring / dependency upgrade
+- [ ] Bug fix (non-breaking change which fixes an issue)
+- [ ] New feature (non-breaking change which adds functionality)
+- [ ] Breaking change (fix or feature that would cause existing functionality to change)
+
+## Checklist
+
+<!--- Go over all the following points, and put an `x` in all the boxes that apply. -->
+<!--- If you're unsure about any of these, don't hesitate to ask. We're here to help! -->
+
+- [ ] My code follows the code style of this project.
+- [ ] My change requires a change to the documentation.
+- [ ] I have updated the documentation accordingly.
+- [ ] I have read the **CONTRIBUTING** document.
+- [ ] I have added tests to cover my changes.
+- [ ] All new and existing tests passed.
--- a/README.md
+++ b/README.md
@ -11,7 +11,7 @@

 ## Introduction

-Excelize is a library written in pure Go and providing a set of functions that allow you to write to and read from XLSX files. Support reads and writes XLSX file generated by Microsoft Excel™ 2007 and later. Support save file without losing original charts of XLSX. This library needs Go version 1.8 or later. The full API docs can be seen using go's built-in documentation tool, or online at [godoc.org](https://godoc.org/github.com/360EntSecGroup-Skylar/excelize) and [Chinese translation](https://xuri.me/excelize/zh_cn).
+Excelize is a library written in pure Go and providing a set of functions that allow you to write to and read from XLSX files. Support reads and writes XLSX file generated by Microsoft Excel™ 2007 and later. Support save file without losing original charts of XLSX. This library needs Go version 1.8 or later. The full API docs can be seen using go's built-in documentation tool, or online at [godoc.org](https://godoc.org/github.com/360EntSecGroup-Skylar/excelize) and [docs reference](https://xuri.me/excelize/).

 ## Basic Usage

--- a/README_zh.md
+++ b/README_zh.md
@ -11,7 +11,7 @@

 ## 简介

-Excelize 是 Go 语言编写的用于操作 Office Excel 文档类库，基于 ECMA-376 Office OpenXML 标准。可以使用它来读取、写入由 Microsoft Excel™ 2007 及以上版本创建的 XLSX 文档。相比较其他的开源类库，Excelize 支持写入原本带有图片(表)、透视表和切片器等复杂样式的文档，还支持向 Excel 文档中插入图片与图表，并且在保存后不会丢失文档原有样式，可以应用于各类报表系统中。使用本类库要求使用的 Go 语言为 1.8 或更高版本，完整的 API 使用文档请访问 [godoc.org](https://godoc.org/github.com/360EntSecGroup-Skylar/excelize) 或查看 [中文翻译](https://xuri.me/excelize/zh_cn)。
+Excelize 是 Go 语言编写的用于操作 Office Excel 文档类库，基于 ECMA-376 Office OpenXML 标准。可以使用它来读取、写入由 Microsoft Excel™ 2007 及以上版本创建的 XLSX 文档。相比较其他的开源类库，Excelize 支持写入原本带有图片(表)、透视表和切片器等复杂样式的文档，还支持向 Excel 文档中插入图片与图表，并且在保存后不会丢失文档原有样式，可以应用于各类报表系统中。使用本类库要求使用的 Go 语言为 1.8 或更高版本，完整的 API 使用文档请访问 [godoc.org](https://godoc.org/github.com/360EntSecGroup-Skylar/excelize) 或查看 [参考文档](https://xuri.me/excelize/)。

 ## 快速上手

--- a/cell.go
+++ b/cell.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import (
@ -20,7 +29,7 @@ const (
 	STCellFormulaTypeShared = "shared"
 )

-// mergeCellsParser provides function to check merged cells in worksheet by
+// mergeCellsParser provides a function to check merged cells in worksheet by
 // given axis.
 func (f *File) mergeCellsParser(xlsx *xlsxWorksheet, axis string) string {
 	axis = strings.ToUpper(axis)
@ -34,8 +43,8 @@ func (f *File) mergeCellsParser(xlsx *xlsxWorksheet, axis string) string {
 	return axis
 }

-// SetCellValue provides function to set value of a cell. The following shows
-// the supported data types:
+// SetCellValue provides a function to set value of a cell. The following
+// shows the supported data types:
 //
 //    int
 //    int8
@ -83,7 +92,7 @@ func (f *File) SetCellValue(sheet, axis string, value interface{}) {
 	}
 }

-// setCellIntValue provides function to set int value of a cell.
+// setCellIntValue provides a function to set int value of a cell.
 func (f *File) setCellIntValue(sheet, axis string, value interface{}) {
 	switch value.(type) {
 	case int:
@ -111,7 +120,7 @@ func (f *File) setCellIntValue(sheet, axis string, value interface{}) {
 	}
 }

-// SetCellBool provides function to set bool type value of a cell by given
+// SetCellBool provides a function to set bool type value of a cell by given
 // worksheet name, cell coordinates and cell value.
 func (f *File) SetCellBool(sheet, axis string, value bool) {
 	xlsx := f.workSheetReader(sheet)
@ -139,10 +148,10 @@ func (f *File) SetCellBool(sheet, axis string, value bool) {
 	}
 }

-// GetCellValue provides function to get formatted value from cell by given
-// worksheet name and axis in XLSX file. If it is possible to apply a format to
-// the cell value, it will do so, if not then an error will be returned, along
-// with the raw value of the cell.
+// GetCellValue provides a function to get formatted value from cell by given
+// worksheet name and axis in XLSX file. If it is possible to apply a format
+// to the cell value, it will do so, if not then an error will be returned,
+// along with the raw value of the cell.
 func (f *File) GetCellValue(sheet, axis string) string {
 	xlsx := f.workSheetReader(sheet)
 	axis = f.mergeCellsParser(xlsx, axis)
@ -174,9 +183,9 @@ func (f *File) GetCellValue(sheet, axis string) string {
 	return ""
 }

-// formattedValue provides function to returns a value after formatted. If it is
-// possible to apply a format to the cell value, it will do so, if not then an
-// error will be returned, along with the raw value of the cell.
+// formattedValue provides a function to returns a value after formatted. If
+// it is possible to apply a format to the cell value, it will do so, if not
+// then an error will be returned, along with the raw value of the cell.
 func (f *File) formattedValue(s int, v string) string {
 	if s == 0 {
 		return v
@ -189,7 +198,7 @@ func (f *File) formattedValue(s int, v string) string {
 	return v
 }

-// GetCellStyle provides function to get cell style index by given worksheet
+// GetCellStyle provides a function to get cell style index by given worksheet
 // name and cell coordinates.
 func (f *File) GetCellStyle(sheet, axis string) int {
 	xlsx := f.workSheetReader(sheet)
@ -211,8 +220,8 @@ func (f *File) GetCellStyle(sheet, axis string) int {
 	return f.prepareCellStyle(xlsx, cell, xlsx.SheetData.Row[xAxis].C[yAxis].S)
 }

-// GetCellFormula provides function to get formula from cell by given worksheet
-// name and axis in XLSX file.
+// GetCellFormula provides a function to get formula from cell by given
+// worksheet name and axis in XLSX file.
 func (f *File) GetCellFormula(sheet, axis string) string {
 	xlsx := f.workSheetReader(sheet)
 	axis = f.mergeCellsParser(xlsx, axis)
@ -276,7 +285,7 @@ func getSharedForumula(xlsx *xlsxWorksheet, si string) string {
 	return ""
 }

-// SetCellFormula provides function to set cell formula by given string and
+// SetCellFormula provides a function to set cell formula by given string and
 // worksheet name.
 func (f *File) SetCellFormula(sheet, axis, formula string) {
 	xlsx := f.workSheetReader(sheet)
@ -305,10 +314,10 @@ func (f *File) SetCellFormula(sheet, axis, formula string) {
 	}
 }

-// SetCellHyperLink provides function to set cell hyperlink by given worksheet
-// name and link URL address. LinkType defines two types of hyperlink "External"
-// for web site or "Location" for moving to one of cell in this workbook. The
-// below is example for external link.
+// SetCellHyperLink provides a function to set cell hyperlink by given
+// worksheet name and link URL address. LinkType defines two types of
+// hyperlink "External" for web site or "Location" for moving to one of cell
+// in this workbook. The below is example for external link.
 //
 //    xlsx.SetCellHyperLink("Sheet1", "A3", "https://github.com/360EntSecGroup-Skylar/excelize", "External")
 //    // Set underline and font color style for the cell.
@ -341,10 +350,10 @@ func (f *File) SetCellHyperLink(sheet, axis, link, linkType string) {
 	xlsx.Hyperlinks.Hyperlink = append(xlsx.Hyperlinks.Hyperlink, hyperlink)
 }

-// GetCellHyperLink provides function to get cell hyperlink by given worksheet
-// name and axis. Boolean type value link will be ture if the cell has a
-// hyperlink and the target is the address of the hyperlink. Otherwise, the
-// value of link will be false and the value of the target will be a blank
+// GetCellHyperLink provides a function to get cell hyperlink by given
+// worksheet name and axis. Boolean type value link will be ture if the cell
+// has a hyperlink and the target is the address of the hyperlink. Otherwise,
+// the value of link will be false and the value of the target will be a blank
 // string. For example get hyperlink of Sheet1!H6:
 //
 //    link, target := xlsx.GetCellHyperLink("Sheet1", "H6")
@ -369,8 +378,8 @@ func (f *File) GetCellHyperLink(sheet, axis string) (bool, string) {
 	return link, target
 }

-// MergeCell provides function to merge cells by given coordinate area and sheet
-// name. For example create a merged cell of D3:E9 on Sheet1:
+// MergeCell provides a function to merge cells by given coordinate area and
+// sheet name. For example create a merged cell of D3:E9 on Sheet1:
 //
 //    xlsx.MergeCell("Sheet1", "D3", "E9")
 //
@ -429,7 +438,7 @@ func (f *File) MergeCell(sheet, hcell, vcell string) {
 	}
 }

-// SetCellInt provides function to set int type value of a cell by given
+// SetCellInt provides a function to set int type value of a cell by given
 // worksheet name, cell coordinates and cell value.
 func (f *File) SetCellInt(sheet, axis string, value int) {
 	xlsx := f.workSheetReader(sheet)
@ -453,7 +462,7 @@ func (f *File) SetCellInt(sheet, axis string, value int) {
 	xlsx.SheetData.Row[xAxis].C[yAxis].V = strconv.Itoa(value)
 }

-// prepareCellStyle provides function to prepare style index of cell in
+// prepareCellStyle provides a function to prepare style index of cell in
 // worksheet by given column index and style index.
 func (f *File) prepareCellStyle(xlsx *xlsxWorksheet, col, style int) int {
 	if xlsx.Cols != nil && style == 0 {
@ -466,8 +475,8 @@ func (f *File) prepareCellStyle(xlsx *xlsxWorksheet, col, style int) int {
 	return style
 }

-// SetCellStr provides function to set string type value of a cell. Total number
-// of characters that a cell can contain 32767 characters.
+// SetCellStr provides a function to set string type value of a cell. Total
+// number of characters that a cell can contain 32767 characters.
 func (f *File) SetCellStr(sheet, axis, value string) {
 	xlsx := f.workSheetReader(sheet)
 	axis = f.mergeCellsParser(xlsx, axis)
@ -502,7 +511,7 @@ func (f *File) SetCellStr(sheet, axis, value string) {
 	xlsx.SheetData.Row[xAxis].C[yAxis].V = value
 }

-// SetCellDefault provides function to set string type value of a cell as
+// SetCellDefault provides a function to set string type value of a cell as
 // default format without escaping the cell.
 func (f *File) SetCellDefault(sheet, axis, value string) {
 	xlsx := f.workSheetReader(sheet)
@ -567,7 +576,7 @@ func (f *File) SetSheetRow(sheet, axis string, slice interface{}) {
 	}
 }

-// checkCellInArea provides function to determine if a given coordinate is
+// checkCellInArea provides a function to determine if a given coordinate is
 // within an area.
 func checkCellInArea(cell, area string) bool {
 	cell = strings.ToUpper(cell)
--- a/chart.go
+++ b/chart.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import (
@ -190,7 +199,7 @@ var (
 	}
 )

-// parseFormatChartSet provides function to parse the format settings of the
+// parseFormatChartSet provides a function to parse the format settings of the
 // chart with default value.
 func parseFormatChartSet(formatSet string) (*formatChart, error) {
 	format := formatChart{
@ -352,7 +361,9 @@ func parseFormatChartSet(formatSet string) (*formatChart, error) {
 //    minimum
 //
 // reverse_order: Specifies that the categories or values on reverse order (orientation of the chart). The reverse_order property is optional. The default value is false.
+//
 // maximum: Specifies that the fixed maximum, 0 is auto. The maximum property is optional. The default value is auto.
+//
 // minimum: Specifies that the fixed minimum, 0 is auto. The minimum property is optional. The default value is auto.
 //
 // Set chart size by dimension property. The dimension property is optional. The default width is 480, and height is 290.
@ -377,7 +388,7 @@ func (f *File) AddChart(sheet, cell, format string) error {
 	return err
 }

-// countCharts provides function to get chart files count storage in the
+// countCharts provides a function to get chart files count storage in the
 // folder xl/charts.
 func (f *File) countCharts() int {
 	count := 0
@ -389,7 +400,7 @@ func (f *File) countCharts() int {
 	return count
 }

-// prepareDrawing provides function to prepare drawing ID and XML by given
+// prepareDrawing provides a function to prepare drawing ID and XML by given
 // drawingID, worksheet name and default drawingXML.
 func (f *File) prepareDrawing(xlsx *xlsxWorksheet, drawingID int, sheet, drawingXML string) (int, string) {
 	sheetRelationshipsDrawingXML := "../drawings/drawing" + strconv.Itoa(drawingID) + ".xml"
@ -406,8 +417,8 @@ func (f *File) prepareDrawing(xlsx *xlsxWorksheet, drawingID int, sheet, drawing
 	return drawingID, drawingXML
 }

-// addChart provides function to create chart as xl/charts/chart%d.xml by given
-// format sets.
+// addChart provides a function to create chart as xl/charts/chart%d.xml by
+// given format sets.
 func (f *File) addChart(formatSet *formatChart) {
 	count := f.countCharts()
 	xlsxChartSpace := xlsxChartSpace{
@ -562,7 +573,7 @@ func (f *File) addChart(formatSet *formatChart) {
 	f.saveFileList(media, chart)
 }

-// drawBaseChart provides function to draw the c:plotArea element for bar,
+// drawBaseChart provides a function to draw the c:plotArea element for bar,
 // and column series charts by given format sets.
 func (f *File) drawBaseChart(formatSet *formatChart) *cPlotArea {
 	c := cCharts{
@ -659,7 +670,7 @@ func (f *File) drawBaseChart(formatSet *formatChart) *cPlotArea {
 	return charts[formatSet.Type]
 }

-// drawDoughnutChart provides function to draw the c:plotArea element for
+// drawDoughnutChart provides a function to draw the c:plotArea element for
 // doughnut chart by given format sets.
 func (f *File) drawDoughnutChart(formatSet *formatChart) *cPlotArea {
 	return &cPlotArea{
@ -673,8 +684,8 @@ func (f *File) drawDoughnutChart(formatSet *formatChart) *cPlotArea {
 	}
 }

-// drawLineChart provides function to draw the c:plotArea element for line chart
-// by given format sets.
+// drawLineChart provides a function to draw the c:plotArea element for line
+// chart by given format sets.
 func (f *File) drawLineChart(formatSet *formatChart) *cPlotArea {
 	return &cPlotArea{
 		LineChart: &cCharts{
@ -699,8 +710,8 @@ func (f *File) drawLineChart(formatSet *formatChart) *cPlotArea {
 	}
 }

-// drawPieChart provides function to draw the c:plotArea element for pie chart
-// by given format sets.
+// drawPieChart provides a function to draw the c:plotArea element for pie
+// chart by given format sets.
 func (f *File) drawPieChart(formatSet *formatChart) *cPlotArea {
 	return &cPlotArea{
 		PieChart: &cCharts{
@ -712,8 +723,8 @@ func (f *File) drawPieChart(formatSet *formatChart) *cPlotArea {
 	}
 }

-// drawPie3DChart provides function to draw the c:plotArea element for 3D pie
-// chart by given format sets.
+// drawPie3DChart provides a function to draw the c:plotArea element for 3D
+// pie chart by given format sets.
 func (f *File) drawPie3DChart(formatSet *formatChart) *cPlotArea {
 	return &cPlotArea{
 		Pie3DChart: &cCharts{
@ -725,7 +736,7 @@ func (f *File) drawPie3DChart(formatSet *formatChart) *cPlotArea {
 	}
 }

-// drawRadarChart provides function to draw the c:plotArea element for radar
+// drawRadarChart provides a function to draw the c:plotArea element for radar
 // chart by given format sets.
 func (f *File) drawRadarChart(formatSet *formatChart) *cPlotArea {
 	return &cPlotArea{
@ -748,8 +759,8 @@ func (f *File) drawRadarChart(formatSet *formatChart) *cPlotArea {
 	}
 }

-// drawScatterChart provides function to draw the c:plotArea element for scatter
-// chart by given format sets.
+// drawScatterChart provides a function to draw the c:plotArea element for
+// scatter chart by given format sets.
 func (f *File) drawScatterChart(formatSet *formatChart) *cPlotArea {
 	return &cPlotArea{
 		ScatterChart: &cCharts{
@ -771,8 +782,8 @@ func (f *File) drawScatterChart(formatSet *formatChart) *cPlotArea {
 	}
 }

-// drawChartSeries provides function to draw the c:ser element by given format
-// sets.
+// drawChartSeries provides a function to draw the c:ser element by given
+// format sets.
 func (f *File) drawChartSeries(formatSet *formatChart) *[]cSer {
 	ser := []cSer{}
 	for k := range formatSet.Series {
@ -797,7 +808,7 @@ func (f *File) drawChartSeries(formatSet *formatChart) *[]cSer {
 	return &ser
 }

-// drawChartSeriesSpPr provides function to draw the c:spPr element by given
+// drawChartSeriesSpPr provides a function to draw the c:spPr element by given
 // format sets.
 func (f *File) drawChartSeriesSpPr(i int, formatSet *formatChart) *cSpPr {
 	spPrScatter := &cSpPr{
@ -819,8 +830,8 @@ func (f *File) drawChartSeriesSpPr(i int, formatSet *formatChart) *cSpPr {
 	return chartSeriesSpPr[formatSet.Type]
 }

-// drawChartSeriesDPt provides function to draw the c:dPt element by given data
-// index and format sets.
+// drawChartSeriesDPt provides a function to draw the c:dPt element by given
+// data index and format sets.
 func (f *File) drawChartSeriesDPt(i int, formatSet *formatChart) []*cDPt {
 	dpt := []*cDPt{{
 		IDx:      &attrValInt{Val: i},
@ -848,8 +859,8 @@ func (f *File) drawChartSeriesDPt(i int, formatSet *formatChart) []*cDPt {
 	return chartSeriesDPt[formatSet.Type]
 }

-// drawChartSeriesCat provides function to draw the c:cat element by given chart
-// series and format sets.
+// drawChartSeriesCat provides a function to draw the c:cat element by given
+// chart series and format sets.
 func (f *File) drawChartSeriesCat(v formatChartSeries, formatSet *formatChart) *cCat {
 	cat := &cCat{
 		StrRef: &cStrRef{
@ -860,8 +871,8 @@ func (f *File) drawChartSeriesCat(v formatChartSeries, formatSet *formatChart) *
 	return chartSeriesCat[formatSet.Type]
 }

-// drawChartSeriesVal provides function to draw the c:val element by given chart
-// series and format sets.
+// drawChartSeriesVal provides a function to draw the c:val element by given
+// chart series and format sets.
 func (f *File) drawChartSeriesVal(v formatChartSeries, formatSet *formatChart) *cVal {
 	val := &cVal{
 		NumRef: &cNumRef{
@ -872,8 +883,8 @@ func (f *File) drawChartSeriesVal(v formatChartSeries, formatSet *formatChart) *
 	return chartSeriesVal[formatSet.Type]
 }

-// drawChartSeriesMarker provides function to draw the c:marker element by given
-// data index and format sets.
+// drawChartSeriesMarker provides a function to draw the c:marker element by
+// given data index and format sets.
 func (f *File) drawChartSeriesMarker(i int, formatSet *formatChart) *cMarker {
 	marker := &cMarker{
 		Symbol: &attrValString{Val: "circle"},
@ -898,7 +909,7 @@ func (f *File) drawChartSeriesMarker(i int, formatSet *formatChart) *cMarker {
 	return chartSeriesMarker[formatSet.Type]
 }

-// drawChartSeriesXVal provides function to draw the c:xVal element by given
+// drawChartSeriesXVal provides a function to draw the c:xVal element by given
 // chart series and format sets.
 func (f *File) drawChartSeriesXVal(v formatChartSeries, formatSet *formatChart) *cCat {
 	cat := &cCat{
@ -910,7 +921,7 @@ func (f *File) drawChartSeriesXVal(v formatChartSeries, formatSet *formatChart)
 	return chartSeriesXVal[formatSet.Type]
 }

-// drawChartSeriesYVal provides function to draw the c:yVal element by given
+// drawChartSeriesYVal provides a function to draw the c:yVal element by given
 // chart series and format sets.
 func (f *File) drawChartSeriesYVal(v formatChartSeries, formatSet *formatChart) *cVal {
 	val := &cVal{
@ -922,8 +933,8 @@ func (f *File) drawChartSeriesYVal(v formatChartSeries, formatSet *formatChart)
 	return chartSeriesYVal[formatSet.Type]
 }

-// drawChartDLbls provides function to draw the c:dLbls element by given format
-// sets.
+// drawChartDLbls provides a function to draw the c:dLbls element by given
+// format sets.
 func (f *File) drawChartDLbls(formatSet *formatChart) *cDLbls {
 	return &cDLbls{
 		ShowLegendKey:   &attrValBool{Val: formatSet.Legend.ShowLegendKey},
@ -936,15 +947,15 @@ func (f *File) drawChartDLbls(formatSet *formatChart) *cDLbls {
 	}
 }

-// drawChartSeriesDLbls provides function to draw the c:dLbls element by given
-// format sets.
+// drawChartSeriesDLbls provides a function to draw the c:dLbls element by
+// given format sets.
 func (f *File) drawChartSeriesDLbls(formatSet *formatChart) *cDLbls {
 	dLbls := f.drawChartDLbls(formatSet)
 	chartSeriesDLbls := map[string]*cDLbls{Bar: dLbls, BarStacked: dLbls, BarPercentStacked: dLbls, Bar3DClustered: dLbls, Bar3DStacked: dLbls, Bar3DPercentStacked: dLbls, Col: dLbls, ColStacked: dLbls, ColPercentStacked: dLbls, Col3DClustered: dLbls, Col3D: dLbls, Col3DStacked: dLbls, Col3DPercentStacked: dLbls, Doughnut: dLbls, Line: dLbls, Pie: dLbls, Pie3D: dLbls, Radar: dLbls, Scatter: nil}
 	return chartSeriesDLbls[formatSet.Type]
 }

-// drawPlotAreaCatAx provides function to draw the c:catAx element.
+// drawPlotAreaCatAx provides a function to draw the c:catAx element.
 func (f *File) drawPlotAreaCatAx(formatSet *formatChart) []*cAxs {
 	min := &attrValFloat{Val: formatSet.XAxis.Minimum}
 	max := &attrValFloat{Val: formatSet.XAxis.Maximum}
@ -983,7 +994,7 @@ func (f *File) drawPlotAreaCatAx(formatSet *formatChart) []*cAxs {
 	}
 }

-// drawPlotAreaValAx provides function to draw the c:valAx element.
+// drawPlotAreaValAx provides a function to draw the c:valAx element.
 func (f *File) drawPlotAreaValAx(formatSet *formatChart) []*cAxs {
 	min := &attrValFloat{Val: formatSet.YAxis.Minimum}
 	max := &attrValFloat{Val: formatSet.YAxis.Maximum}
@ -1019,7 +1030,7 @@ func (f *File) drawPlotAreaValAx(formatSet *formatChart) []*cAxs {
 	}
 }

-// drawPlotAreaSpPr provides function to draw the c:spPr element.
+// drawPlotAreaSpPr provides a function to draw the c:spPr element.
 func (f *File) drawPlotAreaSpPr() *cSpPr {
 	return &cSpPr{
 		Ln: &aLn{
@ -1038,7 +1049,7 @@ func (f *File) drawPlotAreaSpPr() *cSpPr {
 	}
 }

-// drawPlotAreaTxPr provides function to draw the c:txPr element.
+// drawPlotAreaTxPr provides a function to draw the c:txPr element.
 func (f *File) drawPlotAreaTxPr() *cTxPr {
 	return &cTxPr{
 		BodyPr: aBodyPr{
@ -1077,8 +1088,8 @@ func (f *File) drawPlotAreaTxPr() *cTxPr {
 	}
 }

-// drawingParser provides function to parse drawingXML. In order to solve the
-// problem that the label structure is changed after serialization and
+// drawingParser provides a function to parse drawingXML. In order to solve
+// the problem that the label structure is changed after serialization and
 // deserialization, two different structures: decodeWsDr and encodeWsDr are
 // defined.
 func (f *File) drawingParser(drawingXML string, content *xlsxWsDr) int {
@ -1105,8 +1116,8 @@ func (f *File) drawingParser(drawingXML string, content *xlsxWsDr) int {
 	return cNvPrID
 }

-// addDrawingChart provides function to add chart graphic frame by given sheet,
-// drawingXML, cell, width, height, relationship index and format sets.
+// addDrawingChart provides a function to add chart graphic frame by given
+// sheet, drawingXML, cell, width, height, relationship index and format sets.
 func (f *File) addDrawingChart(sheet, drawingXML, cell string, width, height, rID int, formatSet *formatPicture) {
 	cell = strings.ToUpper(cell)
 	fromCol := string(strings.Map(letterOnlyMapF, cell))
--- a/col.go
+++ b/col.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import (
@ -121,8 +130,8 @@ func (f *File) SetColOutlineLevel(sheet, column string, level uint8) {
 	xlsx.Cols.Col = append(xlsx.Cols.Col, col)
 }

-// SetColWidth provides function to set the width of a single column or multiple
-// columns. For example:
+// SetColWidth provides a function to set the width of a single column or
+// multiple columns. For example:
 //
 //    xlsx := excelize.NewFile()
 //    xlsx.SetColWidth("Sheet1", "A", "H", 20)
@ -259,8 +268,8 @@ func (f *File) positionObjectPixels(sheet string, colStart, rowStart, x1, y1, wi
 	return colStart, rowStart, xAbs, yAbs, colEnd, rowEnd, x2, y2
 }

-// getColWidth provides function to get column width in pixels by given sheet
-// name and column index.
+// getColWidth provides a function to get column width in pixels by given
+// sheet name and column index.
 func (f *File) getColWidth(sheet string, col int) int {
 	xlsx := f.workSheetReader(sheet)
 	if xlsx.Cols != nil {
@ -278,8 +287,8 @@ func (f *File) getColWidth(sheet string, col int) int {
 	return int(defaultColWidthPixels)
 }

-// GetColWidth provides function to get column width by given worksheet name and
-// column index.
+// GetColWidth provides a function to get column width by given worksheet name
+// and column index.
 func (f *File) GetColWidth(sheet, column string) float64 {
 	col := TitleToNumber(strings.ToUpper(column)) + 1
 	xlsx := f.workSheetReader(sheet)
@ -298,8 +307,8 @@ func (f *File) GetColWidth(sheet, column string) float64 {
 	return defaultColWidthPixels
 }

-// InsertCol provides function to insert a new column before given column index.
-// For example, create a new column before column C in Sheet1:
+// InsertCol provides a function to insert a new column before given column
+// index. For example, create a new column before column C in Sheet1:
 //
 //    xlsx.InsertCol("Sheet1", "C")
 //
@ -308,8 +317,8 @@ func (f *File) InsertCol(sheet, column string) {
 	f.adjustHelper(sheet, col, -1, 1)
 }

-// RemoveCol provides function to remove single column by given worksheet name
-// and column index. For example, remove column C in Sheet1:
+// RemoveCol provides a function to remove single column by given worksheet
+// name and column index. For example, remove column C in Sheet1:
 //
 //    xlsx.RemoveCol("Sheet1", "C")
 //
@ -346,10 +355,10 @@ func completeCol(xlsx *xlsxWorksheet, row, cell int) {
 	}
 }

-// convertColWidthToPixels provieds function to convert the width of a cell from
-// user's units to pixels. Excel rounds the column width to the nearest pixel.
-// If the width hasn't been set by the user we use the default value. If the
-// column is hidden it has a value of zero.
+// convertColWidthToPixels provieds function to convert the width of a cell
+// from user's units to pixels. Excel rounds the column width to the nearest
+// pixel. If the width hasn't been set by the user we use the default value.
+// If the column is hidden it has a value of zero.
 func convertColWidthToPixels(width float64) float64 {
 	var padding float64 = 5
 	var pixels float64
--- a/comment.go
+++ b/comment.go
@ -1,14 +1,24 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import (
 	"encoding/json"
 	"encoding/xml"
+	"fmt"
 	"strconv"
 	"strings"
 )

-// parseFormatCommentsSet provides function to parse the format settings of the
-// comment with default value.
+// parseFormatCommentsSet provides a function to parse the format settings of
+// the comment with default value.
 func parseFormatCommentsSet(formatSet string) (*formatComment, error) {
 	format := formatComment{
 		Author: "Author:",
@ -18,6 +28,36 @@ func parseFormatCommentsSet(formatSet string) (*formatComment, error) {
 	return &format, err
 }

+// GetComments retrieves all comments and returns a map of worksheet name to
+// the worksheet comments.
+func (f *File) GetComments() (comments map[string][]Comment) {
+	comments = map[string][]Comment{}
+	for n := range f.sheetMap {
+		commentID := f.GetSheetIndex(n)
+		commentsXML := "xl/comments" + strconv.Itoa(commentID) + ".xml"
+		c, ok := f.XLSX[commentsXML]
+		if ok {
+			d := xlsxComments{}
+			xml.Unmarshal([]byte(c), &d)
+			sheetComments := []Comment{}
+			for _, comment := range d.CommentList.Comment {
+				sheetComment := Comment{}
+				if comment.AuthorID < len(d.Authors) {
+					sheetComment.Author = d.Authors[comment.AuthorID].Author
+				}
+				sheetComment.Ref = comment.Ref
+				sheetComment.AuthorID = comment.AuthorID
+				for _, text := range comment.Text.R {
+					sheetComment.Text += text.T
+				}
+				sheetComments = append(sheetComments, sheetComment)
+			}
+			comments[n] = sheetComments
+		}
+	}
+	return
+}
+
 // AddComment provides the method to add comment in a sheet by given worksheet
 // index, cell and format set (such as author and text). Note that the max
 // author length is 255 and the max text length is 32512. For example, add a
@ -49,14 +89,23 @@ func (f *File) AddComment(sheet, cell, format string) error {
 	}
 	commentsXML := "xl/comments" + strconv.Itoa(commentID) + ".xml"
 	f.addComment(commentsXML, cell, formatSet)
-	f.addDrawingVML(commentID, drawingVML, cell)
+	var colCount int
+	for i, l := range strings.Split(formatSet.Text, "\n") {
+		if ll := len(l); ll > colCount {
+			if i == 0 {
+				ll += len(formatSet.Author)
+			}
+			colCount = ll
+		}
+	}
+	f.addDrawingVML(commentID, drawingVML, cell, strings.Count(formatSet.Text, "\n")+1, colCount)
 	f.addContentTypePart(commentID, "comments")
 	return err
 }

-// addDrawingVML provides function to create comment as
+// addDrawingVML provides a function to create comment as
 // xl/drawings/vmlDrawing%d.vml by given commit ID and cell.
-func (f *File) addDrawingVML(commentID int, drawingVML, cell string) {
+func (f *File) addDrawingVML(commentID int, drawingVML, cell string, lineCount, colCount int) {
 	col := string(strings.Map(letterOnlyMapF, cell))
 	row, _ := strconv.Atoi(strings.Map(intOnlyMapF, cell))
 	xAxis := row - 1
@ -83,7 +132,7 @@ func (f *File) addDrawingVML(commentID int, drawingVML, cell string) {
 			},
 			VPath: &vPath{
 				Gradientshapeok: "t",
-				Connecttype:     "rect",
+				Connecttype:     "miter",
 			},
 		},
 	}
@ -113,10 +162,12 @@ func (f *File) addDrawingVML(commentID int, drawingVML, cell string) {
 		},
 		ClientData: &xClientData{
 			ObjectType: "Note",
-			Anchor:     "3, 15, 8, 6, 4, 54, 13, 2",
-			AutoFill:   "False",
-			Row:        xAxis,
-			Column:     yAxis,
+			Anchor: fmt.Sprintf(
+				"%d, 23, %d, 0, %d, %d, %d, 5",
+				1+yAxis, 1+xAxis, 2+yAxis+lineCount, colCount+yAxis, 2+xAxis+lineCount),
+			AutoFill: "True",
+			Row:      xAxis,
+			Column:   yAxis,
 		},
 	}
 	s, _ := xml.Marshal(sp)
@ -149,8 +200,8 @@ func (f *File) addDrawingVML(commentID int, drawingVML, cell string) {
 	f.XLSX[drawingVML] = v
 }

-// addComment provides function to create chart as xl/comments%d.xml by given
-// cell and format sets.
+// addComment provides a function to create chart as xl/comments%d.xml by
+// given cell and format sets.
 func (f *File) addComment(commentsXML, cell string, formatSet *formatComment) {
 	a := formatSet.Author
 	t := formatSet.Text
@ -209,8 +260,8 @@ func (f *File) addComment(commentsXML, cell string, formatSet *formatComment) {
 	f.saveFileList(commentsXML, v)
 }

-// countComments provides function to get comments files count storage in the
-// folder xl.
+// countComments provides a function to get comments files count storage in
+// the folder xl.
 func (f *File) countComments() int {
 	count := 0
 	for k := range f.XLSX {
--- a/datavalidation.go
+++ b/datavalidation.go
@ -0,0 +1,233 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
+package excelize
+
+import (
+	"fmt"
+	"strings"
+)
+
+// DataValidationType defined the type of data validation.
+type DataValidationType int
+
+// Data validation types.
+const (
+	_DataValidationType = iota
+	typeNone            // inline use
+	DataValidationTypeCustom
+	DataValidationTypeDate
+	DataValidationTypeDecimal
+	typeList // inline use
+	DataValidationTypeTextLeng
+	DataValidationTypeTime
+	// DataValidationTypeWhole Integer
+	DataValidationTypeWhole
+)
+
+const (
+	// dataValidationFormulaStrLen 255 characters+ 2 quotes
+	dataValidationFormulaStrLen = 257
+	// dataValidationFormulaStrLenErr
+	dataValidationFormulaStrLenErr = "data validation must be 0-255 characters"
+)
+
+// DataValidationErrorStyle defined the style of data validation error alert.
+type DataValidationErrorStyle int
+
+// Data validation error styles.
+const (
+	_ DataValidationErrorStyle = iota
+	DataValidationErrorStyleStop
+	DataValidationErrorStyleWarning
+	DataValidationErrorStyleInformation
+)
+
+// Data validation error styles.
+const (
+	styleStop        = "stop"
+	styleWarning     = "warning"
+	styleInformation = "information"
+)
+
+// DataValidationOperator operator enum.
+type DataValidationOperator int
+
+// Data validation operators.
+const (
+	_DataValidationOperator = iota
+	DataValidationOperatorBetween
+	DataValidationOperatorEqual
+	DataValidationOperatorGreaterThan
+	DataValidationOperatorGreaterThanOrEqual
+	DataValidationOperatorLessThan
+	DataValidationOperatorLessThanOrEqual
+	DataValidationOperatorNotBetween
+	DataValidationOperatorNotEqual
+)
+
+// NewDataValidation return data validation struct.
+func NewDataValidation(allowBlank bool) *DataValidation {
+	return &DataValidation{
+		AllowBlank:       allowBlank,
+		ShowErrorMessage: false,
+		ShowInputMessage: false,
+	}
+}
+
+// SetError set error notice.
+func (dd *DataValidation) SetError(style DataValidationErrorStyle, title, msg string) {
+	dd.Error = &msg
+	dd.ErrorTitle = &title
+	strStyle := styleStop
+	switch style {
+	case DataValidationErrorStyleStop:
+		strStyle = styleStop
+	case DataValidationErrorStyleWarning:
+		strStyle = styleWarning
+	case DataValidationErrorStyleInformation:
+		strStyle = styleInformation
+
+	}
+	dd.ShowErrorMessage = true
+	dd.ErrorStyle = &strStyle
+}
+
+// SetInput set prompt notice.
+func (dd *DataValidation) SetInput(title, msg string) {
+	dd.ShowInputMessage = true
+	dd.PromptTitle = &title
+	dd.Prompt = &msg
+}
+
+// SetDropList data validation list.
+func (dd *DataValidation) SetDropList(keys []string) error {
+	dd.Formula1 = "\"" + strings.Join(keys, ",") + "\""
+	dd.Type = convDataValidationType(typeList)
+	return nil
+}
+
+// SetRange provides function to set data validation range in drop list.
+func (dd *DataValidation) SetRange(f1, f2 int, t DataValidationType, o DataValidationOperator) error {
+	formula1 := fmt.Sprintf("%d", f1)
+	formula2 := fmt.Sprintf("%d", f2)
+	if dataValidationFormulaStrLen < len(dd.Formula1) || dataValidationFormulaStrLen < len(dd.Formula2) {
+		return fmt.Errorf(dataValidationFormulaStrLenErr)
+	}
+
+	dd.Formula1 = formula1
+	dd.Formula2 = formula2
+	dd.Type = convDataValidationType(t)
+	dd.Operator = convDataValidationOperatior(o)
+	return nil
+}
+
+// SetSqrefDropList provides set data validation on a range with source
+// reference range of the worksheet by given data validation object and
+// worksheet name. The data validation object can be created by
+// NewDataValidation function. For example, set data validation on
+// Sheet1!A7:B8 with validation criteria source Sheet1!E1:E3 settings, create
+// in-cell dropdown by allowing list source:
+//
+//     dvRange := excelize.NewDataValidation(true)
+//     dvRange.Sqref = "A7:B8"
+//     dvRange.SetSqrefDropList("E1:E3", true)
+//     xlsx.AddDataValidation("Sheet1", dvRange)
+//
+func (dd *DataValidation) SetSqrefDropList(sqref string, isCurrentSheet bool) error {
+	if isCurrentSheet {
+		dd.Formula1 = sqref
+		dd.Type = convDataValidationType(typeList)
+		return nil
+	}
+	return fmt.Errorf("cross-sheet sqref cell are not supported")
+}
+
+// SetSqref provides function to set data validation range in drop list.
+func (dd *DataValidation) SetSqref(sqref string) {
+	if dd.Sqref == "" {
+		dd.Sqref = sqref
+	} else {
+		dd.Sqref = fmt.Sprintf("%s %s", dd.Sqref, sqref)
+	}
+}
+
+// convDataValidationType get excel data validation type.
+func convDataValidationType(t DataValidationType) string {
+	typeMap := map[DataValidationType]string{
+		typeNone:                   "none",
+		DataValidationTypeCustom:   "custom",
+		DataValidationTypeDate:     "date",
+		DataValidationTypeDecimal:  "decimal",
+		typeList:                   "list",
+		DataValidationTypeTextLeng: "textLength",
+		DataValidationTypeTime:     "time",
+		DataValidationTypeWhole:    "whole",
+	}
+
+	return typeMap[t]
+
+}
+
+// convDataValidationOperatior get excel data validation operator.
+func convDataValidationOperatior(o DataValidationOperator) string {
+	typeMap := map[DataValidationOperator]string{
+		DataValidationOperatorBetween:            "between",
+		DataValidationOperatorEqual:              "equal",
+		DataValidationOperatorGreaterThan:        "greaterThan",
+		DataValidationOperatorGreaterThanOrEqual: "greaterThanOrEqual",
+		DataValidationOperatorLessThan:           "lessThan",
+		DataValidationOperatorLessThanOrEqual:    "lessThanOrEqual",
+		DataValidationOperatorNotBetween:         "notBetween",
+		DataValidationOperatorNotEqual:           "notEqual",
+	}
+
+	return typeMap[o]
+
+}
+
+// AddDataValidation provides set data validation on a range of the worksheet
+// by given data validation object and worksheet name. The data validation
+// object can be created by NewDataValidation function.
+//
+// Example 1, set data validation on Sheet1!A1:B2 with validation criteria
+// settings, show error alert after invalid data is entered with "Stop" style
+// and custom title "error body":
+//
+//     dvRange := excelize.NewDataValidation(true)
+//     dvRange.Sqref = "A1:B2"
+//     dvRange.SetRange(10, 20, excelize.DataValidationTypeWhole, excelize.DataValidationOperatorBetween)
+//     dvRange.SetError(excelize.DataValidationErrorStyleStop, "error title", "error body")
+//     xlsx.AddDataValidation("Sheet1", dvRange)
+//
+// Example 2, set data validation on Sheet1!A3:B4 with validation criteria
+// settings, and show input message when cell is selected:
+//
+//     dvRange = excelize.NewDataValidation(true)
+//     dvRange.Sqref = "A3:B4"
+//     dvRange.SetRange(10, 20, excelize.DataValidationTypeWhole, excelize.DataValidationOperatorGreaterThan)
+//     dvRange.SetInput("input title", "input body")
+//     xlsx.AddDataValidation("Sheet1", dvRange)
+//
+// Example 3, set data validation on Sheet1!A5:B6 with validation criteria
+// settings, create in-cell dropdown by allowing list source:
+//
+//     dvRange = excelize.NewDataValidation(true)
+//     dvRange.Sqref = "A5:B6"
+//     dvRange.SetDropList([]string{"1", "2", "3"})
+//     xlsx.AddDataValidation("Sheet1", dvRange)
+//
+func (f *File) AddDataValidation(sheet string, dv *DataValidation) {
+	xlsx := f.workSheetReader(sheet)
+	if nil == xlsx.DataValidations {
+		xlsx.DataValidations = new(xlsxDataValidations)
+	}
+	xlsx.DataValidations.DataValidation = append(xlsx.DataValidations.DataValidation, dv)
+	xlsx.DataValidations.Count = len(xlsx.DataValidations.DataValidation)
+}
--- a/datavalidation_test.go
+++ b/datavalidation_test.go
@ -0,0 +1,57 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
+package excelize
+
+import "testing"
+
+func TestDataValidation(t *testing.T) {
+	xlsx := NewFile()
+
+	dvRange := NewDataValidation(true)
+	dvRange.Sqref = "A1:B2"
+	dvRange.SetRange(10, 20, DataValidationTypeWhole, DataValidationOperatorBetween)
+	dvRange.SetError(DataValidationErrorStyleStop, "error title", "error body")
+	dvRange.SetError(DataValidationErrorStyleWarning, "error title", "error body")
+	dvRange.SetError(DataValidationErrorStyleInformation, "error title", "error body")
+	xlsx.AddDataValidation("Sheet1", dvRange)
+
+	dvRange = NewDataValidation(true)
+	dvRange.Sqref = "A3:B4"
+	dvRange.SetRange(10, 20, DataValidationTypeWhole, DataValidationOperatorGreaterThan)
+	dvRange.SetInput("input title", "input body")
+	xlsx.AddDataValidation("Sheet1", dvRange)
+
+	dvRange = NewDataValidation(true)
+	dvRange.Sqref = "A5:B6"
+	dvRange.SetDropList([]string{"1", "2", "3"})
+	xlsx.AddDataValidation("Sheet1", dvRange)
+
+	xlsx.SetCellStr("Sheet1", "E1", "E1")
+	xlsx.SetCellStr("Sheet1", "E2", "E2")
+	xlsx.SetCellStr("Sheet1", "E3", "E3")
+	dvRange = NewDataValidation(true)
+	dvRange.SetSqref("A7:B8")
+	dvRange.SetSqref("A7:B8")
+	dvRange.SetSqrefDropList("$E$1:$E$3", true)
+	err := dvRange.SetSqrefDropList("$E$1:$E$3", false)
+	t.Log(err)
+	xlsx.AddDataValidation("Sheet1", dvRange)
+
+	dvRange = NewDataValidation(true)
+	dvRange.SetDropList(make([]string, 258))
+	err = dvRange.SetRange(10, 20, DataValidationTypeWhole, DataValidationOperatorGreaterThan)
+	t.Log(err)
+
+	// Test write file to given path.
+	err = xlsx.SaveAs("./test/Book_data_validation.xlsx")
+	if err != nil {
+		t.Error(err)
+	}
+}
--- a/date.go
+++ b/date.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import (
@ -8,17 +17,31 @@ import (
 // timeLocationUTC defined the UTC time location.
 var timeLocationUTC, _ = time.LoadLocation("UTC")

-// timeToUTCTime provides function to convert time to UTC time.
+// timeToUTCTime provides a function to convert time to UTC time.
 func timeToUTCTime(t time.Time) time.Time {
 	return time.Date(t.Year(), t.Month(), t.Day(), t.Hour(), t.Minute(), t.Second(), t.Nanosecond(), timeLocationUTC)
 }

-// timeToExcelTime provides function to convert time to Excel time.
+// timeToExcelTime provides a function to convert time to Excel time.
 func timeToExcelTime(t time.Time) float64 {
-	return float64(t.UnixNano())/8.64e13 + 25569.0
+	// TODO in future this should probably also handle date1904 and like TimeFromExcelTime
+	var excelTime float64
+	var deltaDays int64
+	excelTime = 0
+	deltaDays = 290 * 364
+	// check if UnixNano would be out of int64 range
+	for t.Unix() > deltaDays*24*60*60 {
+		// reduce by aprox. 290 years, which is max for int64 nanoseconds
+		delta := time.Duration(deltaDays) * 24 * time.Hour
+		excelTime = excelTime + float64(deltaDays)
+		t = t.Add(-delta)
+	}
+	// finally add remainder of UnixNano to keep nano precision
+	// and 25569 which is days between 1900 and 1970
+	return excelTime + float64(t.UnixNano())/8.64e13 + 25569.0
 }

-// shiftJulianToNoon provides function to process julian date to noon.
+// shiftJulianToNoon provides a function to process julian date to noon.
 func shiftJulianToNoon(julianDays, julianFraction float64) (float64, float64) {
 	switch {
 	case -0.5 < julianFraction && julianFraction < 0.5:
@ -33,7 +56,7 @@ func shiftJulianToNoon(julianDays, julianFraction float64) (float64, float64) {
 	return julianDays, julianFraction
 }

-// fractionOfADay provides function to return the integer values for hour,
+// fractionOfADay provides a function to return the integer values for hour,
 // minutes, seconds and nanoseconds that comprised a given fraction of a day.
 // values would round to 1 us.
 func fractionOfADay(fraction float64) (hours, minutes, seconds, nanoseconds int) {
@ -54,7 +77,7 @@ func fractionOfADay(fraction float64) (hours, minutes, seconds, nanoseconds int)
 	return
 }

-// julianDateToGregorianTime provides function to convert julian date to
+// julianDateToGregorianTime provides a function to convert julian date to
 // gregorian time.
 func julianDateToGregorianTime(part1, part2 float64) time.Time {
 	part1I, part1F := math.Modf(part1)
@ -67,12 +90,12 @@ func julianDateToGregorianTime(part1, part2 float64) time.Time {
 	return time.Date(year, time.Month(month), day, hours, minutes, seconds, nanoseconds, time.UTC)
 }

-// By this point generations of programmers have repeated the algorithm sent to
-// the editor of "Communications of the ACM" in 1968 (published in CACM, volume
-// 11, number 10, October 1968, p.657). None of those programmers seems to have
-// found it necessary to explain the constants or variable names set out by
-// Henry F. Fliegel and Thomas C. Van Flandern.  Maybe one day I'll buy that
-// jounal and expand an explanation here - that day is not today.
+// By this point generations of programmers have repeated the algorithm sent
+// to the editor of "Communications of the ACM" in 1968 (published in CACM,
+// volume 11, number 10, October 1968, p.657). None of those programmers seems
+// to have found it necessary to explain the constants or variable names set
+// out by Henry F. Fliegel and Thomas C. Van Flandern.  Maybe one day I'll buy
+// that jounal and expand an explanation here - that day is not today.
 func doTheFliegelAndVanFlandernAlgorithm(jd int) (day, month, year int) {
 	l := jd + 68569
 	n := (4 * l) / 146097
@ -87,9 +110,10 @@ func doTheFliegelAndVanFlandernAlgorithm(jd int) (day, month, year int) {
 	return d, m, y
 }

-// timeFromExcelTime provides function to convert an excelTime representation
-// (stored as a floating point number) to a time.Time.
+// timeFromExcelTime provides a function to convert an excelTime
+// representation (stored as a floating point number) to a time.Time.
 func timeFromExcelTime(excelTime float64, date1904 bool) time.Time {
+	const MDD int64 = 106750 // Max time.Duration Days, aprox. 290 years
 	var date time.Time
 	var intPart = int64(excelTime)
 	// Excel uses Julian dates prior to March 1st 1900, and Gregorian
@ -113,6 +137,13 @@ func timeFromExcelTime(excelTime float64, date1904 bool) time.Time {
 	} else {
 		date = time.Date(1899, 12, 30, 0, 0, 0, 0, time.UTC)
 	}
+
+	// Duration is limited to aprox. 290 years
+	for intPart > MDD {
+		durationDays := time.Duration(MDD) * time.Hour * 24
+		date = date.Add(durationDays)
+		intPart = intPart - MDD
+	}
 	durationDays := time.Duration(intPart) * time.Hour * 24
 	durationPart := time.Duration(dayNanoSeconds * floatPart)
 	return date.Add(durationDays).Add(durationPart)
--- a/date_test.go
+++ b/date_test.go
@ -0,0 +1,42 @@
+package excelize
+
+import (
+	"testing"
+	"time"
+)
+
+type dateTest struct {
+	ExcelValue float64
+	GoValue    time.Time
+}
+
+func TestTimeToExcelTime(t *testing.T) {
+	trueExpectedInputList := []dateTest{
+		{0.0, time.Date(1899, 12, 30, 0, 0, 0, 0, time.UTC)},
+		{25569.0, time.Unix(0, 0)},
+		{43269.0, time.Date(2018, 6, 18, 0, 0, 0, 0, time.UTC)},
+		{401769.0, time.Date(3000, 1, 1, 0, 0, 0, 0, time.UTC)},
+	}
+
+	for _, test := range trueExpectedInputList {
+		if test.ExcelValue != timeToExcelTime(test.GoValue) {
+			t.Fatalf("Expected %v from %v = true, got %v\n", test.ExcelValue, test.GoValue, timeToExcelTime(test.GoValue))
+		}
+	}
+}
+
+func TestTimeFromExcelTime(t *testing.T) {
+	trueExpectedInputList := []dateTest{
+		{0.0, time.Date(1899, 12, 30, 0, 0, 0, 0, time.UTC)},
+		{60.0, time.Date(1900, 2, 28, 0, 0, 0, 0, time.UTC)},
+		{61.0, time.Date(1900, 3, 1, 0, 0, 0, 0, time.UTC)},
+		{41275.0, time.Date(2013, 1, 1, 0, 0, 0, 0, time.UTC)},
+		{401769.0, time.Date(3000, 1, 1, 0, 0, 0, 0, time.UTC)},
+	}
+
+	for _, test := range trueExpectedInputList {
+		if test.GoValue != timeFromExcelTime(test.ExcelValue, false) {
+			t.Fatalf("Expected %v from %v = true, got %v\n", test.GoValue, test.ExcelValue, timeFromExcelTime(test.ExcelValue, false))
+		}
+	}
+}
--- a/excelize.go
+++ b/excelize.go
@ -1,3 +1,13 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+//
+// See https://xuri.me/excelize for more information about this package.
 package excelize

 import (
@ -21,6 +31,7 @@ type File struct {
 	Sheet         map[string]*xlsxWorksheet
 	SheetCount    int
 	Styles        *xlsxStyleSheet
+	Theme         *xlsxTheme
 	WorkBook      *xlsxWorkbook
 	WorkBookRels  *xlsxWorkbookRels
 	XLSX          map[string][]byte
@ -66,10 +77,11 @@ func OpenReader(r io.Reader) (*File, error) {
 	}
 	f.sheetMap = f.getSheetMap()
 	f.Styles = f.stylesReader()
+	f.Theme = f.themeReader()
 	return f, nil
 }

-// setDefaultTimeStyle provides function to set default numbers format for
+// setDefaultTimeStyle provides a function to set default numbers format for
 // time.Time type cell value by given worksheet name, cell coordinates and
 // number format code.
 func (f *File) setDefaultTimeStyle(sheet, axis string, format int) {
@ -79,8 +91,8 @@ func (f *File) setDefaultTimeStyle(sheet, axis string, format int) {
 	}
 }

-// workSheetReader provides function to get the pointer to the structure after
-// deserialization by given worksheet name.
+// workSheetReader provides a function to get the pointer to the structure
+// after deserialization by given worksheet name.
 func (f *File) workSheetReader(sheet string) *xlsxWorksheet {
 	name, ok := f.sheetMap[trimSheetName(sheet)]
 	if !ok {
@ -103,7 +115,7 @@ func (f *File) workSheetReader(sheet string) *xlsxWorksheet {
 	return f.Sheet[name]
 }

-// checkSheet provides function to fill each row element and make that is
+// checkSheet provides a function to fill each row element and make that is
 // continuous in a worksheet of XML.
 func checkSheet(xlsx *xlsxWorksheet) {
 	row := len(xlsx.SheetData.Row)
@ -131,7 +143,7 @@ func checkSheet(xlsx *xlsxWorksheet) {
 	xlsx.SheetData = sheetData
 }

-// replaceWorkSheetsRelationshipsNameSpaceBytes provides function to replace
+// replaceWorkSheetsRelationshipsNameSpaceBytes provides a function to replace
 // xl/worksheets/sheet%d.xml XML tags to self-closing for compatible Microsoft
 // Office Excel 2007.
 func replaceWorkSheetsRelationshipsNameSpaceBytes(workbookMarshal []byte) []byte {
@ -180,7 +192,7 @@ func (f *File) UpdateLinkedValue() {
 	}
 }

-// adjustHelper provides function to adjust rows and columns dimensions,
+// adjustHelper provides a function to adjust rows and columns dimensions,
 // hyperlinks, merged cells and auto filter when inserting or deleting rows or
 // columns.
 //
@ -202,7 +214,7 @@ func (f *File) adjustHelper(sheet string, column, row, offset int) {
 	checkRow(xlsx)
 }

-// adjustColDimensions provides function to update column dimensions when
+// adjustColDimensions provides a function to update column dimensions when
 // inserting or deleting rows or columns.
 func (f *File) adjustColDimensions(xlsx *xlsxWorksheet, column, offset int) {
 	for i, r := range xlsx.SheetData.Row {
@ -218,8 +230,8 @@ func (f *File) adjustColDimensions(xlsx *xlsxWorksheet, column, offset int) {
 	}
 }

-// adjustRowDimensions provides function to update row dimensions when inserting
-// or deleting rows or columns.
+// adjustRowDimensions provides a function to update row dimensions when
+// inserting or deleting rows or columns.
 func (f *File) adjustRowDimensions(xlsx *xlsxWorksheet, rowIndex, offset int) {
 	if rowIndex == -1 {
 		return
@ -238,7 +250,7 @@ func (f *File) adjustRowDimensions(xlsx *xlsxWorksheet, rowIndex, offset int) {
 	}
 }

-// adjustHyperlinks provides function to update hyperlinks when inserting or
+// adjustHyperlinks provides a function to update hyperlinks when inserting or
 // deleting rows or columns.
 func (f *File) adjustHyperlinks(sheet string, column, rowIndex, offset int) {
 	xlsx := f.workSheetReader(sheet)
@ -278,8 +290,8 @@ func (f *File) adjustHyperlinks(sheet string, column, rowIndex, offset int) {
 	}
 }

-// adjustMergeCellsHelper provides function to update merged cells when inserting or
-// deleting rows or columns.
+// adjustMergeCellsHelper provides a function to update merged cells when
+// inserting or deleting rows or columns.
 func (f *File) adjustMergeCellsHelper(xlsx *xlsxWorksheet, column, rowIndex, offset int) {
 	if xlsx.MergeCells != nil {
 		for k, v := range xlsx.MergeCells.Cells {
@ -319,8 +331,8 @@ func (f *File) adjustMergeCellsHelper(xlsx *xlsxWorksheet, column, rowIndex, off
 	}
 }

-// adjustMergeCells provides function to update merged cells when inserting or
-// deleting rows or columns.
+// adjustMergeCells provides a function to update merged cells when inserting
+// or deleting rows or columns.
 func (f *File) adjustMergeCells(xlsx *xlsxWorksheet, column, rowIndex, offset int) {
 	f.adjustMergeCellsHelper(xlsx, column, rowIndex, offset)

@ -340,8 +352,8 @@ func (f *File) adjustMergeCells(xlsx *xlsxWorksheet, column, rowIndex, offset in
 	}
 }

-// adjustAutoFilter provides function to update the auto filter when inserting
-// or deleting rows or columns.
+// adjustAutoFilter provides a function to update the auto filter when
+// inserting or deleting rows or columns.
 func (f *File) adjustAutoFilter(xlsx *xlsxWorksheet, column, rowIndex, offset int) {
 	f.adjustAutoFilterHelper(xlsx, column, rowIndex, offset)

@ -374,7 +386,7 @@ func (f *File) adjustAutoFilter(xlsx *xlsxWorksheet, column, rowIndex, offset in
 	}
 }

-// adjustAutoFilterHelper provides function to update the auto filter when
+// adjustAutoFilterHelper provides a function to update the auto filter when
 // inserting or deleting rows or columns.
 func (f *File) adjustAutoFilterHelper(xlsx *xlsxWorksheet, column, rowIndex, offset int) {
 	if xlsx.AutoFilter != nil {
--- a/excelize_test.go
+++ b/excelize_test.go
@ -2,6 +2,7 @@ package excelize

 import (
 	"fmt"
+	"image/color"
 	_ "image/gif"
 	_ "image/jpeg"
 	_ "image/png"
@ -88,7 +89,6 @@ func TestOpenFile(t *testing.T) {
 	xlsx.SetCellValue("Sheet2", "F16", true)
 	xlsx.SetCellValue("Sheet2", "F17", complex64(5+10i))
 	t.Log(letterOnlyMapF('x'))
-	t.Log(deepCopy(nil, nil))
 	shiftJulianToNoon(1, -0.6)
 	timeFromExcelTime(61, true)
 	timeFromExcelTime(62, true)
@ -162,6 +162,24 @@ func TestAddPicture(t *testing.T) {
 	if err != nil {
 		t.Log(err)
 	}
+	err = xlsx.AddPictureFromBytes("Sheet1", "G21", "", "Excel Logo", "jpg", make([]byte, 1))
+	if err != nil {
+		t.Log(err)
+	}
+	// Test add picture to worksheet with invalid file data.
+	err = xlsx.AddPictureFromBytes("Sheet1", "G21", "", "Excel Logo", ".jpg", make([]byte, 1))
+	if err != nil {
+		t.Log(err)
+	}
+	file, err := ioutil.ReadFile("./test/images/excel.jpg")
+	if err != nil {
+		t.Error(err)
+	}
+	// Test add picture to worksheet from bytes.
+	err = xlsx.AddPictureFromBytes("Sheet1", "Q1", "", "Excel Logo", ".jpg", file)
+	if err != nil {
+		t.Log(err)
+	}
 	// Test write file to given path.
 	err = xlsx.SaveAs("./test/Book2.xlsx")
 	if err != nil {
@ -211,8 +229,13 @@ func TestNewFile(t *testing.T) {
 	if err != nil {
 		t.Error(err)
 	}
-	// Test add picture to worksheet with invalid formatset
+	// Test add picture to worksheet without formatset.
 	err = xlsx.AddPicture("Sheet1", "C2", "./test/images/excel.png", "")
+	if err != nil {
+		t.Error(err)
+	}
+	// Test add picture to worksheet with invalid formatset.
+	err = xlsx.AddPicture("Sheet1", "C2", "./test/images/excel.png", `{`)
 	if err != nil {
 		t.Log(err)
 	}
@ -771,10 +794,6 @@ func TestAddTable(t *testing.T) {
 	if err != nil {
 		t.Error(err)
 	}
-	err = xlsx.AddTable("Sheet2", "A2", "B5", ``)
-	if err != nil {
-		t.Log(err)
-	}
 	err = xlsx.AddTable("Sheet2", "A2", "B5", `{"table_name":"table","table_style":"TableStyleMedium2", "show_first_column":true,"show_last_column":true,"show_row_stripes":false,"show_column_stripes":true}`)
 	if err != nil {
 		t.Error(err)
@ -817,6 +836,11 @@ func TestAddComments(t *testing.T) {
 	if err != nil {
 		t.Error(err)
 	}
+	allComments := xlsx.GetComments()
+	if len(allComments) != 2 {
+		t.Error("Expected 2 comment entry elements.")
+	}
+
 }

 func TestAutoFilter(t *testing.T) {
@ -1146,6 +1170,31 @@ func TestOutlineLevel(t *testing.T) {
 	xlsx.SetColOutlineLevel("Sheet2", "B", 2)
 }

+func TestThemeColor(t *testing.T) {
+	t.Log(ThemeColor("000000", -0.1))
+	t.Log(ThemeColor("000000", 0))
+	t.Log(ThemeColor("000000", 1))
+}
+
+func TestHSL(t *testing.T) {
+	var hsl HSL
+	t.Log(hsl.RGBA())
+	t.Log(hslModel(hsl))
+	t.Log(hslModel(color.Gray16{Y: uint16(1)}))
+	t.Log(HSLToRGB(0, 1, 0.4))
+	t.Log(HSLToRGB(0, 1, 0.6))
+	t.Log(hueToRGB(0, 0, -1))
+	t.Log(hueToRGB(0, 0, 2))
+	t.Log(hueToRGB(0, 0, 1.0/7))
+	t.Log(hueToRGB(0, 0, 0.4))
+	t.Log(hueToRGB(0, 0, 2.0/4))
+	t.Log(RGBToHSL(255, 255, 0))
+	t.Log(RGBToHSL(0, 255, 255))
+	t.Log(RGBToHSL(250, 100, 50))
+	t.Log(RGBToHSL(50, 100, 250))
+	t.Log(RGBToHSL(250, 50, 100))
+}
+
 func trimSliceSpace(s []string) []string {
 	for {
 		if len(s) > 0 && s[len(s)-1] == "" {
--- a/file.go
+++ b/file.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import (
@ -8,7 +17,7 @@ import (
 	"os"
 )

-// NewFile provides function to create new file by default template. For
+// NewFile provides a function to create new file by default template. For
 // example:
 //
 //    xlsx := NewFile()
@ -36,19 +45,20 @@ func NewFile() *File {
 	f.WorkBookRels = f.workbookRelsReader()
 	f.Sheet["xl/worksheets/sheet1.xml"] = f.workSheetReader("Sheet1")
 	f.sheetMap["Sheet1"] = "xl/worksheets/sheet1.xml"
+	f.Theme = f.themeReader()
 	return f
 }

-// Save provides function to override the xlsx file with origin path.
+// Save provides a function to override the xlsx file with origin path.
 func (f *File) Save() error {
 	if f.Path == "" {
-		return fmt.Errorf("No path defined for file, consider File.WriteTo or File.Write")
+		return fmt.Errorf("no path defined for file, consider File.WriteTo or File.Write")
 	}
 	return f.SaveAs(f.Path)
 }

-// SaveAs provides function to create or update to an xlsx file at the provided
-// path.
+// SaveAs provides a function to create or update to an xlsx file at the
+// provided path.
 func (f *File) SaveAs(name string) error {
 	file, err := os.OpenFile(name, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0666)
 	if err != nil {
@ -58,8 +68,14 @@ func (f *File) SaveAs(name string) error {
 	return f.Write(file)
 }

-// Write provides function to write to an io.Writer.
+// Write provides a function to write to an io.Writer.
 func (f *File) Write(w io.Writer) error {
+	_, err := f.WriteTo(w)
+	return err
+}
+
+// WriteTo implements io.WriterTo to write the file.
+func (f *File) WriteTo(w io.Writer) (int64, error) {
 	buf := new(bytes.Buffer)
 	zw := zip.NewWriter(buf)
 	f.contentTypesWriter()
@ -70,21 +86,17 @@ func (f *File) Write(w io.Writer) error {
 	for path, content := range f.XLSX {
 		fi, err := zw.Create(path)
 		if err != nil {
-			return err
+			return 0, err
 		}
 		_, err = fi.Write(content)
 		if err != nil {
-			return err
+			return 0, err
 		}
 	}
 	err := zw.Close()
 	if err != nil {
-		return err
+		return 0, err
 	}

-	if _, err := buf.WriteTo(w); err != nil {
-		return err
-	}
-
-	return nil
+	return buf.WriteTo(w)
 }
--- a/hsl.go
+++ b/hsl.go
@ -0,0 +1,139 @@
+// Copyright (c) 2012 Rodrigo Moraes. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// 	 * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+// 	 * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+// 	 * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+package excelize
+
+import (
+	"image/color"
+	"math"
+)
+
+// HSLModel converts any color.Color to a HSL color.
+var HSLModel = color.ModelFunc(hslModel)
+
+// HSL represents a cylindrical coordinate of points in an RGB color model.
+//
+// Values are in the range 0 to 1.
+type HSL struct {
+	H, S, L float64
+}
+
+// RGBA returns the alpha-premultiplied red, green, blue and alpha values
+// for the HSL.
+func (c HSL) RGBA() (uint32, uint32, uint32, uint32) {
+	r, g, b := HSLToRGB(c.H, c.S, c.L)
+	return uint32(r) * 0x101, uint32(g) * 0x101, uint32(b) * 0x101, 0xffff
+}
+
+// hslModel converts a color.Color to HSL.
+func hslModel(c color.Color) color.Color {
+	if _, ok := c.(HSL); ok {
+		return c
+	}
+	r, g, b, _ := c.RGBA()
+	h, s, l := RGBToHSL(uint8(r>>8), uint8(g>>8), uint8(b>>8))
+	return HSL{h, s, l}
+}
+
+// RGBToHSL converts an RGB triple to a HSL triple.
+func RGBToHSL(r, g, b uint8) (h, s, l float64) {
+	fR := float64(r) / 255
+	fG := float64(g) / 255
+	fB := float64(b) / 255
+	max := math.Max(math.Max(fR, fG), fB)
+	min := math.Min(math.Min(fR, fG), fB)
+	l = (max + min) / 2
+	if max == min {
+		// Achromatic.
+		h, s = 0, 0
+	} else {
+		// Chromatic.
+		d := max - min
+		if l > 0.5 {
+			s = d / (2.0 - max - min)
+		} else {
+			s = d / (max + min)
+		}
+		switch max {
+		case fR:
+			h = (fG - fB) / d
+			if fG < fB {
+				h += 6
+			}
+		case fG:
+			h = (fB-fR)/d + 2
+		case fB:
+			h = (fR-fG)/d + 4
+		}
+		h /= 6
+	}
+	return
+}
+
+// HSLToRGB converts an HSL triple to a RGB triple.
+func HSLToRGB(h, s, l float64) (r, g, b uint8) {
+	var fR, fG, fB float64
+	if s == 0 {
+		fR, fG, fB = l, l, l
+	} else {
+		var q float64
+		if l < 0.5 {
+			q = l * (1 + s)
+		} else {
+			q = l + s - s*l
+		}
+		p := 2*l - q
+		fR = hueToRGB(p, q, h+1.0/3)
+		fG = hueToRGB(p, q, h)
+		fB = hueToRGB(p, q, h-1.0/3)
+	}
+	r = uint8((fR * 255) + 0.5)
+	g = uint8((fG * 255) + 0.5)
+	b = uint8((fB * 255) + 0.5)
+	return
+}
+
+// hueToRGB is a helper function for HSLToRGB.
+func hueToRGB(p, q, t float64) float64 {
+	if t < 0 {
+		t++
+	}
+	if t > 1 {
+		t--
+	}
+	if t < 1.0/6 {
+		return p + (q-p)*6*t
+	}
+	if t < 0.5 {
+		return q
+	}
+	if t < 2.0/3 {
+		return p + (q-p)*(2.0/3-t)*6
+	}
+	return p
+}
--- a/lib.go
+++ b/lib.go
@ -1,9 +1,17 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import (
 	"archive/zip"
 	"bytes"
-	"encoding/gob"
 	"io"
 	"log"
 	"math"
@ -26,7 +34,7 @@ func ReadZipReader(r *zip.Reader) (map[string][]byte, int, error) {
 	return fileList, worksheets, nil
 }

-// readXML provides function to read XML content as string.
+// readXML provides a function to read XML content as string.
 func (f *File) readXML(name string) []byte {
 	if content, ok := f.XLSX[name]; ok {
 		return content
@ -34,8 +42,8 @@ func (f *File) readXML(name string) []byte {
 	return []byte{}
 }

-// saveFileList provides function to update given file content in file list of
-// XLSX.
+// saveFileList provides a function to update given file content in file list
+// of XLSX.
 func (f *File) saveFileList(name string, content []byte) {
 	newContent := make([]byte, 0, len(XMLHeader)+len(content))
 	newContent = append(newContent, []byte(XMLHeader)...)
@ -55,7 +63,7 @@ func readFile(file *zip.File) []byte {
 	return buff.Bytes()
 }

-// ToAlphaString provides function to convert integer to Excel sheet column
+// ToAlphaString provides a function to convert integer to Excel sheet column
 // title. For example convert 36 to column title AK:
 //
 //     excelize.ToAlphaString(36)
@ -73,9 +81,9 @@ func ToAlphaString(value int) string {
 	return ans
 }

-// TitleToNumber provides function to convert Excel sheet column title to int
-// (this function doesn't do value check currently). For example convert AK
-// and ak to column title 36:
+// TitleToNumber provides a function to convert Excel sheet column title to
+// int (this function doesn't do value check currently). For example convert
+// AK and ak to column title 36:
 //
 //    excelize.TitleToNumber("AK")
 //    excelize.TitleToNumber("ak")
@ -115,17 +123,6 @@ func intOnlyMapF(rune rune) rune {
 	return -1
 }

-// deepCopy provides method to creates a deep copy of whatever is passed to it
-// and returns the copy in an interface. The returned value will need to be
-// asserted to the correct type.
-func deepCopy(dst, src interface{}) error {
-	var buf bytes.Buffer
-	if err := gob.NewEncoder(&buf).Encode(src); err != nil {
-		return err
-	}
-	return gob.NewDecoder(bytes.NewBuffer(buf.Bytes())).Decode(dst)
-}
-
 // boolPtr returns a pointer to a bool with the given value.
 func boolPtr(b bool) *bool { return &b }

@ -137,8 +134,8 @@ func defaultTrue(b *bool) bool {
 	return *b
 }

-// axisLowerOrEqualThan returns true if axis1 <= axis2
-// axis1/axis2 can be either a column or a row axis, e.g. "A", "AAE", "42", "1", etc.
+// axisLowerOrEqualThan returns true if axis1 <= axis2 axis1/axis2 can be
+// either a column or a row axis, e.g. "A", "AAE", "42", "1", etc.
 //
 // For instance, the following comparisons are all true:
 //
@ -159,7 +156,8 @@ func axisLowerOrEqualThan(axis1, axis2 string) bool {
 	}
 }

-// getCellColRow returns the two parts of a cell identifier (its col and row) as strings
+// getCellColRow returns the two parts of a cell identifier (its col and row)
+// as strings
 //
 // For instance:
 //
@ -176,3 +174,12 @@ func getCellColRow(cell string) (col, row string) {

 	return cell, ""
 }
+
+// parseFormatSet provides a method to convert format string to []byte and
+// handle empty string.
+func parseFormatSet(formatSet string) []byte {
+	if formatSet != "" {
+		return []byte(formatSet)
+	}
+	return []byte("{}")
+}
--- a/picture.go
+++ b/picture.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import (
@ -14,8 +23,8 @@ import (
 	"strings"
 )

-// parseFormatPictureSet provides function to parse the format settings of the
-// picture with default value.
+// parseFormatPictureSet provides a function to parse the format settings of
+// the picture with default value.
 func parseFormatPictureSet(formatSet string) (*formatPicture, error) {
 	format := formatPicture{
 		FPrintsWithSheet: true,
@ -26,7 +35,7 @@ func parseFormatPictureSet(formatSet string) (*formatPicture, error) {
 		XScale:           1.0,
 		YScale:           1.0,
 	}
-	err := json.Unmarshal([]byte(formatSet), &format)
+	err := json.Unmarshal(parseFormatSet(formatSet), &format)
 	return &format, err
 }

@ -78,23 +87,66 @@ func parseFormatPictureSet(formatSet string) (*formatPicture, error) {
 // positioning is move and size with cells.
 func (f *File) AddPicture(sheet, cell, picture, format string) error {
 	var err error
-	var drawingHyperlinkRID int
-	var hyperlinkType string
 	// Check picture exists first.
 	if _, err = os.Stat(picture); os.IsNotExist(err) {
 		return err
 	}
 	ext, ok := supportImageTypes[path.Ext(picture)]
 	if !ok {
-		return errors.New("Unsupported image extension")
+		return errors.New("unsupported image extension")
+	}
+	file, _ := ioutil.ReadFile(picture)
+	_, name := filepath.Split(picture)
+	return f.AddPictureFromBytes(sheet, cell, format, name, ext, file)
+}
+
+// AddPictureFromBytes provides the method to add picture in a sheet by given
+// picture format set (such as offset, scale, aspect ratio setting and print
+// settings), file base name, extension name and file bytes. For example:
+//
+//    package main
+//
+//    import (
+//        "fmt"
+//        _ "image/jpeg"
+//        "io/ioutil"
+//
+//        "github.com/360EntSecGroup-Skylar/excelize"
+//    )
+//
+//    func main() {
+//        xlsx := excelize.NewFile()
+//
+//        file, err := ioutil.ReadFile("./image1.jpg")
+//        if err != nil {
+//            fmt.Println(err)
+//        }
+//        err = xlsx.AddPictureFromBytes("Sheet1", "A2", "", "Excel Logo", ".jpg", file)
+//        if err != nil {
+//            fmt.Println(err)
+//        }
+//        err = xlsx.SaveAs("./Book1.xlsx")
+//        if err != nil {
+//            fmt.Println(err)
+//        }
+//    }
+//
+func (f *File) AddPictureFromBytes(sheet, cell, format, name, extension string, file []byte) error {
+	var err error
+	var drawingHyperlinkRID int
+	var hyperlinkType string
+	ext, ok := supportImageTypes[extension]
+	if !ok {
+		return errors.New("unsupported image extension")
 	}
-	readFile, _ := os.Open(picture)
-	image, _, _ := image.DecodeConfig(readFile)
-	_, file := filepath.Split(picture)
 	formatSet, err := parseFormatPictureSet(format)
 	if err != nil {
 		return err
 	}
+	image, _, err := image.DecodeConfig(bytes.NewReader(file))
+	if err != nil {
+		return err
+	}
 	// Read sheet data.
 	xlsx := f.workSheetReader(sheet)
 	// Add first picture for given sheet, create xl/drawings/ and xl/drawings/_rels/ folder.
@ -110,13 +162,13 @@ func (f *File) AddPicture(sheet, cell, picture, format string) error {
 		}
 		drawingHyperlinkRID = f.addDrawingRelationships(drawingID, SourceRelationshipHyperLink, formatSet.Hyperlink, hyperlinkType)
 	}
-	f.addDrawingPicture(sheet, drawingXML, cell, file, image.Width, image.Height, drawingRID, drawingHyperlinkRID, formatSet)
-	f.addMedia(picture, ext)
+	f.addDrawingPicture(sheet, drawingXML, cell, name, image.Width, image.Height, drawingRID, drawingHyperlinkRID, formatSet)
+	f.addMedia(file, ext)
 	f.addContentTypePart(drawingID, "drawings")
 	return err
 }

-// addSheetRelationships provides function to add
+// addSheetRelationships provides a function to add
 // xl/worksheets/_rels/sheet%d.xml.rels by given worksheet name, relationship
 // type and target.
 func (f *File) addSheetRelationships(sheet, relType, target, targetMode string) int {
@ -149,9 +201,9 @@ func (f *File) addSheetRelationships(sheet, relType, target, targetMode string)
 	return rID
 }

-// deleteSheetRelationships provides function to delete relationships in
-// xl/worksheets/_rels/sheet%d.xml.rels by given worksheet name and relationship
-// index.
+// deleteSheetRelationships provides a function to delete relationships in
+// xl/worksheets/_rels/sheet%d.xml.rels by given worksheet name and
+// relationship index.
 func (f *File) deleteSheetRelationships(sheet, rID string) {
 	name, ok := f.sheetMap[trimSheetName(sheet)]
 	if !ok {
@ -169,7 +221,7 @@ func (f *File) deleteSheetRelationships(sheet, rID string) {
 	f.saveFileList(rels, output)
 }

-// addSheetLegacyDrawing provides function to add legacy drawing element to
+// addSheetLegacyDrawing provides a function to add legacy drawing element to
 // xl/worksheets/sheet%d.xml by given worksheet name and relationship index.
 func (f *File) addSheetLegacyDrawing(sheet string, rID int) {
 	xlsx := f.workSheetReader(sheet)
@ -178,7 +230,7 @@ func (f *File) addSheetLegacyDrawing(sheet string, rID int) {
 	}
 }

-// addSheetDrawing provides function to add drawing element to
+// addSheetDrawing provides a function to add drawing element to
 // xl/worksheets/sheet%d.xml by given worksheet name and relationship index.
 func (f *File) addSheetDrawing(sheet string, rID int) {
 	xlsx := f.workSheetReader(sheet)
@ -187,7 +239,7 @@ func (f *File) addSheetDrawing(sheet string, rID int) {
 	}
 }

-// addSheetPicture provides function to add picture element to
+// addSheetPicture provides a function to add picture element to
 // xl/worksheets/sheet%d.xml by given worksheet name and relationship index.
 func (f *File) addSheetPicture(sheet string, rID int) {
 	xlsx := f.workSheetReader(sheet)
@ -196,7 +248,7 @@ func (f *File) addSheetPicture(sheet string, rID int) {
 	}
 }

-// countDrawings provides function to get drawing files count storage in the
+// countDrawings provides a function to get drawing files count storage in the
 // folder xl/drawings.
 func (f *File) countDrawings() int {
 	count := 0
@ -208,7 +260,7 @@ func (f *File) countDrawings() int {
 	return count
 }

-// addDrawingPicture provides function to add picture by given sheet,
+// addDrawingPicture provides a function to add picture by given sheet,
 // drawingXML, cell, file name, width, height relationship index and format
 // sets.
 func (f *File) addDrawingPicture(sheet, drawingXML, cell, file string, width, height, rID, hyperlinkRID int, formatSet *formatPicture) {
@ -263,8 +315,8 @@ func (f *File) addDrawingPicture(sheet, drawingXML, cell, file string, width, he
 	f.saveFileList(drawingXML, output)
 }

-// addDrawingRelationships provides function to add image part relationships in
-// the file xl/drawings/_rels/drawing%d.xml.rels by given drawing index,
+// addDrawingRelationships provides a function to add image part relationships
+// in the file xl/drawings/_rels/drawing%d.xml.rels by given drawing index,
 // relationship type and target.
 func (f *File) addDrawingRelationships(index int, relType, target, targetMode string) int {
 	var rels = "xl/drawings/_rels/drawing" + strconv.Itoa(index) + ".xml.rels"
@ -292,8 +344,8 @@ func (f *File) addDrawingRelationships(index int, relType, target, targetMode st
 	return rID
 }

-// countMedia provides function to get media files count storage in the folder
-// xl/media/image.
+// countMedia provides a function to get media files count storage in the
+// folder xl/media/image.
 func (f *File) countMedia() int {
 	count := 0
 	for k := range f.XLSX {
@ -304,17 +356,16 @@ func (f *File) countMedia() int {
 	return count
 }

-// addMedia provides function to add picture into folder xl/media/image by given
-// file name and extension name.
-func (f *File) addMedia(file, ext string) {
+// addMedia provides a function to add picture into folder xl/media/image by
+// given file and extension name.
+func (f *File) addMedia(file []byte, ext string) {
 	count := f.countMedia()
-	dat, _ := ioutil.ReadFile(file)
 	media := "xl/media/image" + strconv.Itoa(count+1) + ext
-	f.XLSX[media] = dat
+	f.XLSX[media] = file
 }

-// setContentTypePartImageExtensions provides function to set the content type
-// for relationship parts and the Main Document part.
+// setContentTypePartImageExtensions provides a function to set the content
+// type for relationship parts and the Main Document part.
 func (f *File) setContentTypePartImageExtensions() {
 	var imageTypes = map[string]bool{"jpeg": false, "png": false, "gif": false}
 	content := f.contentTypesReader()
@ -334,7 +385,7 @@ func (f *File) setContentTypePartImageExtensions() {
 	}
 }

-// setContentTypePartVMLExtensions provides function to set the content type
+// setContentTypePartVMLExtensions provides a function to set the content type
 // for relationship parts and the Main Document part.
 func (f *File) setContentTypePartVMLExtensions() {
 	vml := false
@ -352,8 +403,8 @@ func (f *File) setContentTypePartVMLExtensions() {
 	}
 }

-// addContentTypePart provides function to add content type part relationships
-// in the file [Content_Types].xml by given index.
+// addContentTypePart provides a function to add content type part
+// relationships in the file [Content_Types].xml by given index.
 func (f *File) addContentTypePart(index int, contentType string) {
 	setContentType := map[string]func(){
 		"comments": f.setContentTypePartVMLExtensions,
@ -387,7 +438,7 @@ func (f *File) addContentTypePart(index int, contentType string) {
 	})
 }

-// getSheetRelationshipsTargetByID provides function to get Target attribute
+// getSheetRelationshipsTargetByID provides a function to get Target attribute
 // value in xl/worksheets/_rels/sheet%d.xml.rels by given worksheet name and
 // relationship index.
 func (f *File) getSheetRelationshipsTargetByID(sheet, rID string) string {
@ -406,9 +457,9 @@ func (f *File) getSheetRelationshipsTargetByID(sheet, rID string) string {
 	return ""
 }

-// GetPicture provides function to get picture base name and raw content embed
-// in XLSX by given worksheet and cell name. This function returns the file name
-// in XLSX and file contents as []byte data types. For example:
+// GetPicture provides a function to get picture base name and raw content
+// embed in XLSX by given worksheet and cell name. This function returns the
+// file name in XLSX and file contents as []byte data types. For example:
 //
 //    xlsx, err := excelize.OpenFile("./Book1.xlsx")
 //    if err != nil {
@ -463,8 +514,9 @@ func (f *File) GetPicture(sheet, cell string) (string, []byte) {
 	return "", []byte{}
 }

-// getDrawingRelationships provides function to get drawing relationships from
-// xl/drawings/_rels/drawing%s.xml.rels by given file name and relationship ID.
+// getDrawingRelationships provides a function to get drawing relationships
+// from xl/drawings/_rels/drawing%s.xml.rels by given file name and
+// relationship ID.
 func (f *File) getDrawingRelationships(rels, rID string) *xlsxWorkbookRelation {
 	_, ok := f.XLSX[rels]
 	if !ok {
--- a/rows.go
+++ b/rows.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import (
@ -132,7 +141,7 @@ func (err ErrSheetNotExist) Error() string {

 // Rows return a rows iterator. For example:
 //
-//    rows, err := xlsx.GetRows("Sheet1")
+//    rows, err := xlsx.Rows("Sheet1")
 //    for rows.Next() {
 //        for _, colCell := range rows.Columns() {
 //            fmt.Print(colCell, "\t")
@ -202,7 +211,7 @@ func (f *File) SetRowHeight(sheet string, row int, height float64) {
 	xlsx.SheetData.Row[rowIdx].CustomHeight = true
 }

-// getRowHeight provides function to get row height in pixels by given sheet
+// getRowHeight provides a function to get row height in pixels by given sheet
 // name and row index.
 func (f *File) getRowHeight(sheet string, row int) int {
 	xlsx := f.workSheetReader(sheet)
@ -215,7 +224,7 @@ func (f *File) getRowHeight(sheet string, row int) int {
 	return int(defaultRowHeightPixels)
 }

-// GetRowHeight provides function to get row height by given worksheet name
+// GetRowHeight provides a function to get row height by given worksheet name
 // and row index. For example, get the height of the first row in Sheet1:
 //
 //    xlsx.GetRowHeight("Sheet1", 1)
@ -231,7 +240,7 @@ func (f *File) GetRowHeight(sheet string, row int) float64 {
 	return defaultRowHeightPixels
 }

-// sharedStringsReader provides function to get the pointer to the structure
+// sharedStringsReader provides a function to get the pointer to the structure
 // after deserialization of xl/sharedStrings.xml.
 func (f *File) sharedStringsReader() *xlsxSST {
 	if f.SharedStrings == nil {
@ -246,8 +255,9 @@ func (f *File) sharedStringsReader() *xlsxSST {
 	return f.SharedStrings
 }

-// getValueFrom return a value from a column/row cell, this function is inteded
-// to be used with for range on rows an argument with the xlsx opened file.
+// getValueFrom return a value from a column/row cell, this function is
+// inteded to be used with for range on rows an argument with the xlsx opened
+// file.
 func (xlsx *xlsxC) getValueFrom(f *File, d *xlsxSST) (string, error) {
 	switch xlsx.T {
 	case "s":
@ -315,9 +325,9 @@ func (f *File) SetRowOutlineLevel(sheet string, rowIndex int, level uint8) {
 	xlsx.SheetData.Row[rowIndex].OutlineLevel = level
 }

-// GetRowOutlineLevel provides a function to get outline level number of a single row by given
-// worksheet name and row index. For example, get outline number of row 2 in
-// Sheet1:
+// GetRowOutlineLevel provides a function to get outline level number of a
+// single row by given worksheet name and row index. For example, get outline
+// number of row 2 in Sheet1:
 //
 //    xlsx.GetRowOutlineLevel("Sheet1", 2)
 //
@ -329,8 +339,8 @@ func (f *File) GetRowOutlineLevel(sheet string, rowIndex int) uint8 {
 	return xlsx.SheetData.Row[rowIndex].OutlineLevel
 }

-// RemoveRow provides function to remove single row by given worksheet name and
-// row index. For example, remove row 3 in Sheet1:
+// RemoveRow provides a function to remove single row by given worksheet name
+// and row index. For example, remove row 3 in Sheet1:
 //
 //    xlsx.RemoveRow("Sheet1", 2)
 //
@ -349,8 +359,8 @@ func (f *File) RemoveRow(sheet string, row int) {
 	}
 }

-// InsertRow provides function to insert a new row before given row index. For
-// example, create a new row before row 3 in Sheet1:
+// InsertRow provides a function to insert a new row before given row index.
+// For example, create a new row before row 3 in Sheet1:
 //
 //    xlsx.InsertRow("Sheet1", 2)
 //
@ -362,8 +372,8 @@ func (f *File) InsertRow(sheet string, row int) {
 	f.adjustHelper(sheet, -1, row, 1)
 }

-// checkRow provides function to check and fill each column element for all rows
-// and make that is continuous in a worksheet of XML. For example:
+// checkRow provides a function to check and fill each column element for all
+// rows and make that is continuous in a worksheet of XML. For example:
 //
 //    <row r="15" spans="1:22" x14ac:dyDescent="0.2">
 //        <c r="A15" s="2" />
@ -416,7 +426,7 @@ func checkRow(xlsx *xlsxWorksheet) {
 	}
 }

-// completeRow provides function to check and fill each column element for a
+// completeRow provides a function to check and fill each column element for a
 // single row and make that is continuous in a worksheet of XML by given row
 // index and axis.
 func completeRow(xlsx *xlsxWorksheet, row, cell int) {
@ -448,9 +458,9 @@ func completeRow(xlsx *xlsxWorksheet, row, cell int) {
 	}
 }

-// convertRowHeightToPixels provides function to convert the height of a cell
-// from user's units to pixels. If the height hasn't been set by the user we use
-// the default value. If the row is hidden it has a value of zero.
+// convertRowHeightToPixels provides a function to convert the height of a
+// cell from user's units to pixels. If the height hasn't been set by the user
+// we use the default value. If the row is hidden it has a value of zero.
 func convertRowHeightToPixels(height float64) float64 {
 	var pixels float64
 	if height == 0 {
--- a/shape.go
+++ b/shape.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import (
@ -7,7 +16,7 @@ import (
 	"strings"
 )

-// parseFormatShapeSet provides function to parse the format settings of the
+// parseFormatShapeSet provides a function to parse the format settings of the
 // shape with default value.
 func parseFormatShapeSet(formatSet string) (*formatShape, error) {
 	format := formatShape{
@ -29,8 +38,8 @@ func parseFormatShapeSet(formatSet string) (*formatShape, error) {

 // AddShape provides the method to add shape in a sheet by given worksheet
 // index, shape format set (such as offset, scale, aspect ratio setting and
-// print settings) and properties set. For example, add text box (rect shape) in
-// Sheet1:
+// print settings) and properties set. For example, add text box (rect shape)
+// in Sheet1:
 //
 //    xlsx.AddShape("Sheet1", "G6", `{"type":"rect","color":{"line":"#4286F4","fill":"#8eb9ff"},"paragraph":[{"text":"Rectangle Shape","font":{"bold":true,"italic":true,"family":"Berlin Sans FB Demi","size":36,"color":"#777777","underline":"sng"}}],"width":180,"height": 90}`)
 //
@ -272,7 +281,7 @@ func (f *File) AddShape(sheet, cell, format string) error {
 	return err
 }

-// addDrawingShape provides function to add preset geometry by given sheet,
+// addDrawingShape provides a function to add preset geometry by given sheet,
 // drawingXMLand format sets.
 func (f *File) addDrawingShape(sheet, drawingXML, cell string, formatSet *formatShape) {
 	textUnderlineType := map[string]bool{"none": true, "words": true, "sng": true, "dbl": true, "heavy": true, "dotted": true, "dottedHeavy": true, "dash": true, "dashHeavy": true, "dashLong": true, "dashLongHeavy": true, "dotDash": true, "dotDashHeavy": true, "dotDotDash": true, "dotDotDashHeavy": true, "wavy": true, "wavyHeavy": true, "wavyDbl": true}
@ -397,7 +406,7 @@ func (f *File) addDrawingShape(sheet, drawingXML, cell string, formatSet *format
 	f.saveFileList(drawingXML, output)
 }

-// setShapeRef provides function to set color with hex model by given actual
+// setShapeRef provides a function to set color with hex model by given actual
 // color value.
 func setShapeRef(color string, i int) *aRef {
 	if color == "" {
--- a/sheet.go
+++ b/sheet.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import (
@ -5,17 +14,19 @@ import (
 	"encoding/json"
 	"encoding/xml"
 	"errors"
+	"io/ioutil"
 	"os"
 	"path"
 	"strconv"
 	"strings"
 	"unicode/utf8"
+
+	"github.com/mohae/deepcopy"
 )

 // NewSheet provides function to create a new sheet by given worksheet name.
-// When creating a new XLSX file, the default sheet will be created.
-// Returns the number of sheets in the workbook (file) after appending the new
-// sheet.
+// When creating a new XLSX file, the default sheet will be created. Returns
+// the number of sheets in the workbook (file) after appending the new sheet.
 func (f *File) NewSheet(name string) int {
 	// Check if the worksheet already exists
 	if f.GetSheetIndex(name) != 0 {
@ -35,7 +46,7 @@ func (f *File) NewSheet(name string) int {
 	return f.SheetCount
 }

-// contentTypesReader provides function to get the pointer to the
+// contentTypesReader provides a function to get the pointer to the
 // [Content_Types].xml structure after deserialization.
 func (f *File) contentTypesReader() *xlsxTypes {
 	if f.ContentTypes == nil {
@ -46,7 +57,7 @@ func (f *File) contentTypesReader() *xlsxTypes {
 	return f.ContentTypes
 }

-// contentTypesWriter provides function to save [Content_Types].xml after
+// contentTypesWriter provides a function to save [Content_Types].xml after
 // serialize structure.
 func (f *File) contentTypesWriter() {
 	if f.ContentTypes != nil {
@ -55,7 +66,7 @@ func (f *File) contentTypesWriter() {
 	}
 }

-// workbookReader provides function to get the pointer to the xl/workbook.xml
+// workbookReader provides a function to get the pointer to the xl/workbook.xml
 // structure after deserialization.
 func (f *File) workbookReader() *xlsxWorkbook {
 	if f.WorkBook == nil {
@ -66,7 +77,7 @@ func (f *File) workbookReader() *xlsxWorkbook {
 	return f.WorkBook
 }

-// workbookWriter provides function to save xl/workbook.xml after serialize
+// workbookWriter provides a function to save xl/workbook.xml after serialize
 // structure.
 func (f *File) workbookWriter() {
 	if f.WorkBook != nil {
@ -75,7 +86,7 @@ func (f *File) workbookWriter() {
 	}
 }

-// worksheetWriter provides function to save xl/worksheets/sheet%d.xml after
+// worksheetWriter provides a function to save xl/worksheets/sheet%d.xml after
 // serialize structure.
 func (f *File) worksheetWriter() {
 	for path, sheet := range f.Sheet {
@ -93,7 +104,7 @@ func (f *File) worksheetWriter() {
 	}
 }

-// trimCell provides function to trim blank cells which created by completeCol.
+// trimCell provides a function to trim blank cells which created by completeCol.
 func trimCell(column []xlsxC) []xlsxC {
 	col := make([]xlsxC, len(column))
 	i := 0
@ -131,14 +142,22 @@ func (f *File) setSheet(index int, name string) {
 // allowed in sheet title.
 func (f *File) setWorkbook(name string, rid int) {
 	content := f.workbookReader()
+	rID := 0
+	for _, v := range content.Sheets.Sheet {
+		t, _ := strconv.Atoi(v.SheetID)
+		if t > rID {
+			rID = t
+		}
+	}
+	rID++
 	content.Sheets.Sheet = append(content.Sheets.Sheet, xlsxSheet{
 		Name:    trimSheetName(name),
-		SheetID: strconv.Itoa(rid),
+		SheetID: strconv.Itoa(rID),
 		ID:      "rId" + strconv.Itoa(rid),
 	})
 }

-// workbookRelsReader provides function to read and unmarshal workbook
+// workbookRelsReader provides a function to read and unmarshal workbook
 // relationships of XLSX file.
 func (f *File) workbookRelsReader() *xlsxWorkbookRels {
 	if f.WorkBookRels == nil {
@ -149,7 +168,7 @@ func (f *File) workbookRelsReader() *xlsxWorkbookRels {
 	return f.WorkBookRels
 }

-// workbookRelsWriter provides function to save xl/_rels/workbook.xml.rels after
+// workbookRelsWriter provides a function to save xl/_rels/workbook.xml.rels after
 // serialize structure.
 func (f *File) workbookRelsWriter() {
 	if f.WorkBookRels != nil {
@ -238,8 +257,8 @@ func (f *File) SetActiveSheet(index int) {
 	}
 }

-// GetActiveSheetIndex provides function to get active sheet index of the XLSX. If not
-// found the active sheet will be return integer 0.
+// GetActiveSheetIndex provides a function to get active sheet index of the
+// XLSX. If not found the active sheet will be return integer 0.
 func (f *File) GetActiveSheetIndex() int {
 	buffer := bytes.Buffer{}
 	content := f.workbookReader()
@ -260,7 +279,7 @@ func (f *File) GetActiveSheetIndex() int {
 	return 0
 }

-// SetSheetName provides function to set the worksheet name be given old and new
+// SetSheetName provides a function to set the worksheet name be given old and new
 // worksheet name. Maximum 31 characters are allowed in sheet title and this
 // function only changes the name of the sheet and will not update the sheet
 // name in the formula or reference associated with the cell. So there may be
@ -278,7 +297,7 @@ func (f *File) SetSheetName(oldName, newName string) {
 	}
 }

-// GetSheetName provides function to get worksheet name of XLSX by given
+// GetSheetName provides a function to get worksheet name of XLSX by given
 // worksheet index. If given sheet index is invalid, will return an empty
 // string.
 func (f *File) GetSheetName(index int) string {
@ -297,7 +316,7 @@ func (f *File) GetSheetName(index int) string {
 	return ""
 }

-// GetSheetIndex provides function to get worksheet index of XLSX by given sheet
+// GetSheetIndex provides a function to get worksheet index of XLSX by given sheet
 // name. If given worksheet name is invalid, will return an integer type value
 // 0.
 func (f *File) GetSheetIndex(name string) int {
@ -316,7 +335,7 @@ func (f *File) GetSheetIndex(name string) int {
 	return 0
 }

-// GetSheetMap provides function to get worksheet name and index map of XLSX.
+// GetSheetMap provides a function to get worksheet name and index map of XLSX.
 // For example:
 //
 //    xlsx, err := excelize.OpenFile("./Book1.xlsx")
@ -342,7 +361,7 @@ func (f *File) GetSheetMap() map[int]string {
 	return sheetMap
 }

-// getSheetMap provides function to get worksheet name and XML file path map of
+// getSheetMap provides a function to get worksheet name and XML file path map of
 // XLSX.
 func (f *File) getSheetMap() map[string]string {
 	maps := make(map[string]string)
@ -352,8 +371,8 @@ func (f *File) getSheetMap() map[string]string {
 	return maps
 }

-// SetSheetBackground provides function to set background picture by given
-// worksheet name.
+// SetSheetBackground provides a function to set background picture by given
+// worksheet name and file path.
 func (f *File) SetSheetBackground(sheet, picture string) error {
 	var err error
 	// Check picture exists first.
@ -362,17 +381,18 @@ func (f *File) SetSheetBackground(sheet, picture string) error {
 	}
 	ext, ok := supportImageTypes[path.Ext(picture)]
 	if !ok {
-		return errors.New("Unsupported image extension")
+		return errors.New("unsupported image extension")
 	}
 	pictureID := f.countMedia() + 1
 	rID := f.addSheetRelationships(sheet, SourceRelationshipImage, "../media/image"+strconv.Itoa(pictureID)+ext, "")
 	f.addSheetPicture(sheet, rID)
-	f.addMedia(picture, ext)
+	file, _ := ioutil.ReadFile(picture)
+	f.addMedia(file, ext)
 	f.setContentTypePartImageExtensions()
 	return err
 }

-// DeleteSheet provides function to delete worksheet in a workbook by given
+// DeleteSheet provides a function to delete worksheet in a workbook by given
 // worksheet name. Use this method with caution, which will affect changes in
 // references such as formulas, charts, and so on. If there is any referenced
 // value of the deleted worksheet, it will cause a file error when you open it.
@ -396,7 +416,7 @@ func (f *File) DeleteSheet(name string) {
 	f.SetActiveSheet(len(f.GetSheetMap()))
 }

-// deleteSheetFromWorkbookRels provides function to remove worksheet
+// deleteSheetFromWorkbookRels provides a function to remove worksheet
 // relationships by given relationships ID in the file
 // xl/_rels/workbook.xml.rels.
 func (f *File) deleteSheetFromWorkbookRels(rID string) string {
@ -410,7 +430,7 @@ func (f *File) deleteSheetFromWorkbookRels(rID string) string {
 	return ""
 }

-// deleteSheetFromContentTypes provides function to remove worksheet
+// deleteSheetFromContentTypes provides a function to remove worksheet
 // relationships by given target name in the file [Content_Types].xml.
 func (f *File) deleteSheetFromContentTypes(target string) {
 	content := f.contentTypesReader()
@ -421,7 +441,7 @@ func (f *File) deleteSheetFromContentTypes(target string) {
 	}
 }

-// CopySheet provides function to duplicate a worksheet by gave source and
+// CopySheet provides a function to duplicate a worksheet by gave source and
 // target worksheet index. Note that currently doesn't support duplicate
 // workbooks that contain tables, charts or pictures. For Example:
 //
@ -432,20 +452,17 @@ func (f *File) deleteSheetFromContentTypes(target string) {
 //
 func (f *File) CopySheet(from, to int) error {
 	if from < 1 || to < 1 || from == to || f.GetSheetName(from) == "" || f.GetSheetName(to) == "" {
-		return errors.New("Invalid worksheet index")
+		return errors.New("invalid worksheet index")
 	}
-	return f.copySheet(from, to)
+	f.copySheet(from, to)
+	return nil
 }

-// copySheet provides function to duplicate a worksheet by gave source and
+// copySheet provides a function to duplicate a worksheet by gave source and
 // target worksheet name.
-func (f *File) copySheet(from, to int) error {
+func (f *File) copySheet(from, to int) {
 	sheet := f.workSheetReader("sheet" + strconv.Itoa(from))
-	worksheet := xlsxWorksheet{}
-	err := deepCopy(&worksheet, &sheet)
-	if err != nil {
-		return err
-	}
+	worksheet := deepcopy.Copy(sheet).(*xlsxWorksheet)
 	path := "xl/worksheets/sheet" + strconv.Itoa(to) + ".xml"
 	if len(worksheet.SheetViews.SheetView) > 0 {
 		worksheet.SheetViews.SheetView[0].TabSelected = false
@ -453,17 +470,16 @@ func (f *File) copySheet(from, to int) error {
 	worksheet.Drawing = nil
 	worksheet.TableParts = nil
 	worksheet.PageSetUp = nil
-	f.Sheet[path] = &worksheet
+	f.Sheet[path] = worksheet
 	toRels := "xl/worksheets/_rels/sheet" + strconv.Itoa(to) + ".xml.rels"
 	fromRels := "xl/worksheets/_rels/sheet" + strconv.Itoa(from) + ".xml.rels"
 	_, ok := f.XLSX[fromRels]
 	if ok {
 		f.XLSX[toRels] = f.XLSX[fromRels]
 	}
-	return err
 }

-// SetSheetVisible provides function to set worksheet visible by given worksheet
+// SetSheetVisible provides a function to set worksheet visible by given worksheet
 // name. A workbook must contain at least one visible worksheet. If the given
 // worksheet has been activated, this setting will be invalidated. Sheet state
 // values as defined by http://msdn.microsoft.com/en-us/library/office/documentformat.openxml.spreadsheet.sheetstatevalues.aspx
@ -505,14 +521,14 @@ func (f *File) SetSheetVisible(name string, visible bool) {
 	}
 }

-// parseFormatPanesSet provides function to parse the panes settings.
+// parseFormatPanesSet provides a function to parse the panes settings.
 func parseFormatPanesSet(formatSet string) (*formatPanes, error) {
 	format := formatPanes{}
 	err := json.Unmarshal([]byte(formatSet), &format)
 	return &format, err
 }

-// SetPanes provides function to create and remove freeze panes and split panes
+// SetPanes provides a function to create and remove freeze panes and split panes
 // by given worksheet name and panes format set.
 //
 // activePane defines the pane that is active. The possible values for this
@ -626,7 +642,7 @@ func (f *File) SetPanes(sheet, panes string) {
 	xlsx.SheetViews.SheetView[len(xlsx.SheetViews.SheetView)-1].Selection = s
 }

-// GetSheetVisible provides function to get worksheet visible by given worksheet
+// GetSheetVisible provides a function to get worksheet visible by given worksheet
 // name. For example, get visible state of Sheet1:
 //
 //    xlsx.GetSheetVisible("Sheet1")
@ -644,7 +660,7 @@ func (f *File) GetSheetVisible(name string) bool {
 	return visible
 }

-// trimSheetName provides function to trim invaild characters by given worksheet
+// trimSheetName provides a function to trim invaild characters by given worksheet
 // name.
 func trimSheetName(name string) string {
 	r := []rune{}
--- a/sheetpr.go
+++ b/sheetpr.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 // SheetPrOption is an option of a view of a worksheet. See SetSheetPrOptions().
@ -98,7 +107,7 @@ func (o *AutoPageBreaks) getSheetPrOption(pr *xlsxSheetPr) {
 	*o = AutoPageBreaks(pr.PageSetUpPr.AutoPageBreaks)
 }

-// SetSheetPrOptions provides function to sets worksheet properties.
+// SetSheetPrOptions provides a function to sets worksheet properties.
 //
 // Available options:
 //   CodeName(string)
@ -120,7 +129,7 @@ func (f *File) SetSheetPrOptions(name string, opts ...SheetPrOption) error {
 	return nil
 }

-// GetSheetPrOptions provides function to gets worksheet properties.
+// GetSheetPrOptions provides a function to gets worksheet properties.
 //
 // Available options:
 //   CodeName(string)
--- a/sheetview.go
+++ b/sheetview.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import "fmt"
--- a/styles.go
+++ b/styles.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import (
@ -10,8 +19,8 @@ import (
 )

 // Excel styles can reference number formats that are built-in, all of which
-// have an id less than 164. This is a possibly incomplete list comprised of as
-// many of them as I could find.
+// have an id less than 164. This is a possibly incomplete list comprised of
+// as many of them as I could find.
 var builtInNumFmt = map[int]string{
 	0:  "general",
 	1:  "0",
@ -798,45 +807,46 @@ var validType = map[string]string{

 // criteriaType defined the list of valid criteria types.
 var criteriaType = map[string]string{
-	"between":      "between",
-	"not between":  "notBetween",
-	"equal to":     "equal",
-	"=":            "equal",
-	"==":           "equal",
-	"not equal to": "notEqual",
-	"!=":           "notEqual",
-	"<>":           "notEqual",
-	"greater than": "greaterThan",
-	">":            "greaterThan",
-	"less than":    "lessThan",
-	"<":            "lessThan",
+	"between":                  "between",
+	"not between":              "notBetween",
+	"equal to":                 "equal",
+	"=":                        "equal",
+	"==":                       "equal",
+	"not equal to":             "notEqual",
+	"!=":                       "notEqual",
+	"<>":                       "notEqual",
+	"greater than":             "greaterThan",
+	">":                        "greaterThan",
+	"less than":                "lessThan",
+	"<":                        "lessThan",
 	"greater than or equal to": "greaterThanOrEqual",
-	">=": "greaterThanOrEqual",
-	"less than or equal to": "lessThanOrEqual",
-	"<=":             "lessThanOrEqual",
-	"containing":     "containsText",
-	"not containing": "notContains",
-	"begins with":    "beginsWith",
-	"ends with":      "endsWith",
-	"yesterday":      "yesterday",
-	"today":          "today",
-	"last 7 days":    "last7Days",
-	"last week":      "lastWeek",
-	"this week":      "thisWeek",
-	"continue week":  "continueWeek",
-	"last month":     "lastMonth",
-	"this month":     "thisMonth",
-	"continue month": "continueMonth",
+	">=":                       "greaterThanOrEqual",
+	"less than or equal to":    "lessThanOrEqual",
+	"<=":                       "lessThanOrEqual",
+	"containing":               "containsText",
+	"not containing":           "notContains",
+	"begins with":              "beginsWith",
+	"ends with":                "endsWith",
+	"yesterday":                "yesterday",
+	"today":                    "today",
+	"last 7 days":              "last7Days",
+	"last week":                "lastWeek",
+	"this week":                "thisWeek",
+	"continue week":            "continueWeek",
+	"last month":               "lastMonth",
+	"this month":               "thisMonth",
+	"continue month":           "continueMonth",
 }

-// formatToString provides function to return original string by given built-in
-// number formats code and cell string.
+// formatToString provides a function to return original string by given
+// built-in number formats code and cell string.
 func formatToString(i int, v string) string {
 	return v
 }

-// formatToInt provides function to convert original string to integer format as
-// string type by given built-in number formats code and cell string.
+// formatToInt provides a function to convert original string to integer
+// format as string type by given built-in number formats code and cell
+// string.
 func formatToInt(i int, v string) string {
 	f, err := strconv.ParseFloat(v, 64)
 	if err != nil {
@ -845,8 +855,9 @@ func formatToInt(i int, v string) string {
 	return fmt.Sprintf("%d", int(f))
 }

-// formatToFloat provides function to convert original string to float format as
-// string type by given built-in number formats code and cell string.
+// formatToFloat provides a function to convert original string to float
+// format as string type by given built-in number formats code and cell
+// string.
 func formatToFloat(i int, v string) string {
 	f, err := strconv.ParseFloat(v, 64)
 	if err != nil {
@ -855,8 +866,8 @@ func formatToFloat(i int, v string) string {
 	return fmt.Sprintf("%.2f", f)
 }

-// formatToA provides function to convert original string to special format as
-// string type by given built-in number formats code and cell string.
+// formatToA provides a function to convert original string to special format
+// as string type by given built-in number formats code and cell string.
 func formatToA(i int, v string) string {
 	f, err := strconv.ParseFloat(v, 64)
 	if err != nil {
@ -870,8 +881,8 @@ func formatToA(i int, v string) string {
 	return fmt.Sprintf("%d", t)
 }

-// formatToB provides function to convert original string to special format as
-// string type by given built-in number formats code and cell string.
+// formatToB provides a function to convert original string to special format
+// as string type by given built-in number formats code and cell string.
 func formatToB(i int, v string) string {
 	f, err := strconv.ParseFloat(v, 64)
 	if err != nil {
@ -883,8 +894,8 @@ func formatToB(i int, v string) string {
 	return fmt.Sprintf("%.2f", f)
 }

-// formatToC provides function to convert original string to special format as
-// string type by given built-in number formats code and cell string.
+// formatToC provides a function to convert original string to special format
+// as string type by given built-in number formats code and cell string.
 func formatToC(i int, v string) string {
 	f, err := strconv.ParseFloat(v, 64)
 	if err != nil {
@ -894,8 +905,8 @@ func formatToC(i int, v string) string {
 	return fmt.Sprintf("%d%%", int(f))
 }

-// formatToD provides function to convert original string to special format as
-// string type by given built-in number formats code and cell string.
+// formatToD provides a function to convert original string to special format
+// as string type by given built-in number formats code and cell string.
 func formatToD(i int, v string) string {
 	f, err := strconv.ParseFloat(v, 64)
 	if err != nil {
@ -905,8 +916,8 @@ func formatToD(i int, v string) string {
 	return fmt.Sprintf("%.2f%%", f)
 }

-// formatToE provides function to convert original string to special format as
-// string type by given built-in number formats code and cell string.
+// formatToE provides a function to convert original string to special format
+// as string type by given built-in number formats code and cell string.
 func formatToE(i int, v string) string {
 	f, err := strconv.ParseFloat(v, 64)
 	if err != nil {
@ -915,17 +926,17 @@ func formatToE(i int, v string) string {
 	return fmt.Sprintf("%.e", f)
 }

-// parseTime provides function to returns a string parsed using time.Time.
+// parseTime provides a function to returns a string parsed using time.Time.
 // Replace Excel placeholders with Go time placeholders. For example, replace
-// yyyy with 2006. These are in a specific order, due to the fact that m is used
-// in month, minute, and am/pm. It would be easier to fix that with regular
-// expressions, but if it's possible to keep this simple it would be easier to
-// maintain. Full-length month and days (e.g. March, Tuesday) have letters in
-// them that would be replaced by other characters below (such as the 'h' in
-// March, or the 'd' in Tuesday) below. First we convert them to arbitrary
-// characters unused in Excel Date formats, and then at the end, turn them to
-// what they should actually be.
-// Based off: http://www.ozgrid.com/Excel/CustomFormats.htm
+// yyyy with 2006. These are in a specific order, due to the fact that m is
+// used in month, minute, and am/pm. It would be easier to fix that with
+// regular expressions, but if it's possible to keep this simple it would be
+// easier to maintain. Full-length month and days (e.g. March, Tuesday) have
+// letters in them that would be replaced by other characters below (such as
+// the 'h' in March, or the 'd' in Tuesday) below. First we convert them to
+// arbitrary characters unused in Excel Date formats, and then at the end,
+// turn them to what they should actually be. Based off:
+// http://www.ozgrid.com/Excel/CustomFormats.htm
 func parseTime(i int, v string) string {
 	f, err := strconv.ParseFloat(v, 64)
 	if err != nil {
@ -983,7 +994,7 @@ func is12HourTime(format string) bool {
 	return strings.Contains(format, "am/pm") || strings.Contains(format, "AM/PM") || strings.Contains(format, "a/p") || strings.Contains(format, "A/P")
 }

-// stylesReader provides function to get the pointer to the structure after
+// stylesReader provides a function to get the pointer to the structure after
 // deserialization of xl/styles.xml.
 func (f *File) stylesReader() *xlsxStyleSheet {
 	if f.Styles == nil {
@ -994,7 +1005,7 @@ func (f *File) stylesReader() *xlsxStyleSheet {
 	return f.Styles
 }

-// styleSheetWriter provides function to save xl/styles.xml after serialize
+// styleSheetWriter provides a function to save xl/styles.xml after serialize
 // structure.
 func (f *File) styleSheetWriter() {
 	if f.Styles != nil {
@ -1003,7 +1014,7 @@ func (f *File) styleSheetWriter() {
 	}
 }

-// parseFormatStyleSet provides function to parse the format settings of the
+// parseFormatStyleSet provides a function to parse the format settings of the
 // cells and conditional formats.
 func parseFormatStyleSet(style string) (*formatStyle, error) {
 	format := formatStyle{
@ -1013,8 +1024,8 @@ func parseFormatStyleSet(style string) (*formatStyle, error) {
 	return &format, err
 }

-// NewStyle provides function to create style for cells by given style format.
-// Note that the color field uses RGB color code.
+// NewStyle provides a function to create style for cells by given style
+// format. Note that the color field uses RGB color code.
 //
 // The following shows the border styles sorted by excelize index number:
 //
@ -1404,7 +1415,7 @@ func parseFormatStyleSet(style string) (*formatStyle, error) {
 //     173   | $ English (New Zealand)
 //     174   | $ English (Singapore)
 //     175   | $ English (Trinidad & Tobago)
-//     176   | $ English (U.S. Vigin Islands)
+//     176   | $ English (U.S. Virgin Islands)
 //     177   | $ English (United States)
 //     178   | $ French (Canada)
 //     179   | $ Hawaiian (United States)
@ -1906,10 +1917,10 @@ func (f *File) NewStyle(style string) (int, error) {
 	return cellXfsID, nil
 }

-// NewConditionalStyle provides function to create style for conditional format
-// by given style format. The parameters are the same as function NewStyle().
-// Note that the color field uses RGB color code and only support to set font,
-// fills, alignment and borders currently.
+// NewConditionalStyle provides a function to create style for conditional
+// format by given style format. The parameters are the same as function
+// NewStyle(). Note that the color field uses RGB color code and only support
+// to set font, fills, alignment and borders currently.
 func (f *File) NewConditionalStyle(style string) (int, error) {
 	s := f.stylesReader()
 	fs, err := parseFormatStyleSet(style)
@ -1935,7 +1946,8 @@ func (f *File) NewConditionalStyle(style string) (int, error) {
 	return s.Dxfs.Count - 1, nil
 }

-// setFont provides function to add font style by given cell format settings.
+// setFont provides a function to add font style by given cell format
+// settings.
 func setFont(formatStyle *formatStyle) *font {
 	fontUnderlineType := map[string]string{"single": "single", "double": "double"}
 	if formatStyle.Font.Size < 1 {
@ -1963,8 +1975,8 @@ func setFont(formatStyle *formatStyle) *font {
 	return &f
 }

-// setNumFmt provides function to check if number format code in the range of
-// built-in values.
+// setNumFmt provides a function to check if number format code in the range
+// of built-in values.
 func setNumFmt(style *xlsxStyleSheet, formatStyle *formatStyle) int {
 	dp := "0."
 	numFmtID := 164 // Default custom number format code from 164.
@ -2011,7 +2023,7 @@ func setNumFmt(style *xlsxStyleSheet, formatStyle *formatStyle) int {
 	return formatStyle.NumFmt
 }

-// setCustomNumFmt provides function to set custom number format code.
+// setCustomNumFmt provides a function to set custom number format code.
 func setCustomNumFmt(style *xlsxStyleSheet, formatStyle *formatStyle) int {
 	nf := xlsxNumFmt{FormatCode: *formatStyle.CustomNumFmt}
 	if style.NumFmts != nil {
@ -2029,7 +2041,7 @@ func setCustomNumFmt(style *xlsxStyleSheet, formatStyle *formatStyle) int {
 	return nf.NumFmtID
 }

-// setLangNumFmt provides function to set number format code with language.
+// setLangNumFmt provides a function to set number format code with language.
 func setLangNumFmt(style *xlsxStyleSheet, formatStyle *formatStyle) int {
 	numFmts, ok := langNumFmt[formatStyle.Lang]
 	if !ok {
@ -2056,8 +2068,8 @@ func setLangNumFmt(style *xlsxStyleSheet, formatStyle *formatStyle) int {
 	return nf.NumFmtID
 }

-// setFills provides function to add fill elements in the styles.xml by given
-// cell format settings.
+// setFills provides a function to add fill elements in the styles.xml by
+// given cell format settings.
 func setFills(formatStyle *formatStyle, fg bool) *xlsxFill {
 	var patterns = []string{
 		"none",
@ -2137,9 +2149,10 @@ func setFills(formatStyle *formatStyle, fg bool) *xlsxFill {
 	return &fill
 }

-// setAlignment provides function to formatting information pertaining to text
-// alignment in cells. There are a variety of choices for how text is aligned
-// both horizontally and vertically, as well as indentation settings, and so on.
+// setAlignment provides a function to formatting information pertaining to
+// text alignment in cells. There are a variety of choices for how text is
+// aligned both horizontally and vertically, as well as indentation settings,
+// and so on.
 func setAlignment(formatStyle *formatStyle) *xlsxAlignment {
 	var alignment xlsxAlignment
 	if formatStyle.Alignment != nil {
@ -2156,7 +2169,7 @@ func setAlignment(formatStyle *formatStyle) *xlsxAlignment {
 	return &alignment
 }

-// setProtection provides function to set protection properties associated
+// setProtection provides a function to set protection properties associated
 // with the cell.
 func setProtection(formatStyle *formatStyle) *xlsxProtection {
 	var protection xlsxProtection
@ -2167,7 +2180,7 @@ func setProtection(formatStyle *formatStyle) *xlsxProtection {
 	return &protection
 }

-// setBorders provides function to add border elements in the styles.xml by
+// setBorders provides a function to add border elements in the styles.xml by
 // given borders format settings.
 func setBorders(formatStyle *formatStyle) *xlsxBorder {
 	var styles = []string{
@ -2219,7 +2232,7 @@ func setBorders(formatStyle *formatStyle) *xlsxBorder {
 	return &border
 }

-// setCellXfs provides function to set describes all of the formatting for a
+// setCellXfs provides a function to set describes all of the formatting for a
 // cell.
 func setCellXfs(style *xlsxStyleSheet, fontID, numFmtID, fillID, borderID int, applyAlignment, applyProtection bool, alignment *xlsxAlignment, protection *xlsxProtection) int {
 	var xf xlsxXf
@ -2246,9 +2259,10 @@ func setCellXfs(style *xlsxStyleSheet, fontID, numFmtID, fillID, borderID int, a
 	return style.CellXfs.Count - 1
 }

-// SetCellStyle provides function to add style attribute for cells by given
+// SetCellStyle provides a function to add style attribute for cells by given
 // worksheet name, coordinate area and style ID. Note that diagonalDown and
-// diagonalUp type border should be use same color in the same coordinate area.
+// diagonalUp type border should be use same color in the same coordinate
+// area.
 //
 // For example create a borders of cell H9 on Sheet1:
 //
@ -2352,9 +2366,10 @@ func (f *File) SetCellStyle(sheet, hcell, vcell string, styleID int) {
 	}
 }

-// SetConditionalFormat provides function to create conditional formatting rule
-// for cell value. Conditional formatting is a feature of Excel which allows you
-// to apply a format to a cell or a range of cells based on certain criteria.
+// SetConditionalFormat provides a function to create conditional formatting
+// rule for cell value. Conditional formatting is a feature of Excel which
+// allows you to apply a format to a cell or a range of cells based on certain
+// criteria.
 //
 // The type option is a required parameter and it has no default value.
 // Allowable type values and their associated parameters are:
@ -2407,7 +2422,7 @@ func (f *File) SetCellStyle(sheet, hcell, vcell string, styleID int) {
 //
 // The criteria parameter is used to set the criteria by which the cell data
 // will be evaluated. It has no default value. The most common criteria as
-// applied to {'type': 'cell'} are:
+// applied to {"type"："cell"} are:
 //
 //    between                  |
 //    not between              |
@ -2606,9 +2621,9 @@ func (f *File) SetConditionalFormat(sheet, area, formatSet string) error {
 	return err
 }

-// drawCondFmtCellIs provides function to create conditional formatting rule for
-// cell value (include between, not between, equal, not equal, greater than and
-// less than) by given priority, criteria type and format settings.
+// drawCondFmtCellIs provides a function to create conditional formatting rule
+// for cell value (include between, not between, equal, not equal, greater
+// than and less than) by given priority, criteria type and format settings.
 func drawCondFmtCellIs(p int, ct string, format *formatConditional) *xlsxCfRule {
 	c := &xlsxCfRule{
 		Priority: p + 1,
@ -2629,8 +2644,8 @@ func drawCondFmtCellIs(p int, ct string, format *formatConditional) *xlsxCfRule
 	return c
 }

-// drawCondFmtTop10 provides function to create conditional formatting rule for
-// top N (default is top 10) by given priority, criteria type and format
+// drawCondFmtTop10 provides a function to create conditional formatting rule
+// for top N (default is top 10) by given priority, criteria type and format
 // settings.
 func drawCondFmtTop10(p int, ct string, format *formatConditional) *xlsxCfRule {
 	c := &xlsxCfRule{
@ -2647,9 +2662,9 @@ func drawCondFmtTop10(p int, ct string, format *formatConditional) *xlsxCfRule {
 	return c
 }

-// drawCondFmtAboveAverage provides function to create conditional formatting
-// rule for above average and below average by given priority, criteria type and
-// format settings.
+// drawCondFmtAboveAverage provides a function to create conditional
+// formatting rule for above average and below average by given priority,
+// criteria type and format settings.
 func drawCondFmtAboveAverage(p int, ct string, format *formatConditional) *xlsxCfRule {
 	return &xlsxCfRule{
 		Priority:     p + 1,
@ -2659,7 +2674,7 @@ func drawCondFmtAboveAverage(p int, ct string, format *formatConditional) *xlsxC
 	}
 }

-// drawCondFmtDuplicateUniqueValues provides function to create conditional
+// drawCondFmtDuplicateUniqueValues provides a function to create conditional
 // formatting rule for duplicate and unique values by given priority, criteria
 // type and format settings.
 func drawCondFmtDuplicateUniqueValues(p int, ct string, format *formatConditional) *xlsxCfRule {
@ -2670,16 +2685,29 @@ func drawCondFmtDuplicateUniqueValues(p int, ct string, format *formatConditiona
 	}
 }

-// drawCondFmtColorScale provides function to create conditional formatting rule
-// for color scale (include 2 color scale and 3 color scale) by given priority,
-// criteria type and format settings.
+// drawCondFmtColorScale provides a function to create conditional formatting
+// rule for color scale (include 2 color scale and 3 color scale) by given
+// priority, criteria type and format settings.
 func drawCondFmtColorScale(p int, ct string, format *formatConditional) *xlsxCfRule {
+	minValue := format.MinValue
+	if minValue == "" {
+		minValue = "0"
+	}
+	maxValue := format.MaxValue
+	if maxValue == "" {
+		maxValue = "0"
+	}
+	midValue := format.MidValue
+	if midValue == "" {
+		midValue = "50"
+	}
+
 	c := &xlsxCfRule{
 		Priority: p + 1,
 		Type:     "colorScale",
 		ColorScale: &xlsxColorScale{
 			Cfvo: []*xlsxCfvo{
-				{Type: format.MinType},
+				{Type: format.MinType, Val: minValue},
 			},
 			Color: []*xlsxColor{
 				{RGB: getPaletteColor(format.MinColor)},
@ -2687,16 +2715,16 @@ func drawCondFmtColorScale(p int, ct string, format *formatConditional) *xlsxCfR
 		},
 	}
 	if validType[format.Type] == "3_color_scale" {
-		c.ColorScale.Cfvo = append(c.ColorScale.Cfvo, &xlsxCfvo{Type: format.MidType, Val: 50})
+		c.ColorScale.Cfvo = append(c.ColorScale.Cfvo, &xlsxCfvo{Type: format.MidType, Val: midValue})
 		c.ColorScale.Color = append(c.ColorScale.Color, &xlsxColor{RGB: getPaletteColor(format.MidColor)})
 	}
-	c.ColorScale.Cfvo = append(c.ColorScale.Cfvo, &xlsxCfvo{Type: format.MaxType})
+	c.ColorScale.Cfvo = append(c.ColorScale.Cfvo, &xlsxCfvo{Type: format.MaxType, Val: maxValue})
 	c.ColorScale.Color = append(c.ColorScale.Color, &xlsxColor{RGB: getPaletteColor(format.MaxColor)})
 	return c
 }

-// drawCondFmtDataBar provides function to create conditional formatting rule
-// for data bar by given priority, criteria type and format settings.
+// drawCondFmtDataBar provides a function to create conditional formatting
+// rule for data bar by given priority, criteria type and format settings.
 func drawCondFmtDataBar(p int, ct string, format *formatConditional) *xlsxCfRule {
 	return &xlsxCfRule{
 		Priority: p + 1,
@ -2708,8 +2736,8 @@ func drawCondFmtDataBar(p int, ct string, format *formatConditional) *xlsxCfRule
 	}
 }

-// drawConfFmtExp provides function to create conditional formatting rule for
-// expression by given priority, criteria type and format settings.
+// drawConfFmtExp provides a function to create conditional formatting rule
+// for expression by given priority, criteria type and format settings.
 func drawConfFmtExp(p int, ct string, format *formatConditional) *xlsxCfRule {
 	return &xlsxCfRule{
 		Priority: p + 1,
@ -2719,7 +2747,34 @@ func drawConfFmtExp(p int, ct string, format *formatConditional) *xlsxCfRule {
 	}
 }

-// getPaletteColor provides function to convert the RBG color by given string.
+// getPaletteColor provides a function to convert the RBG color by given
+// string.
 func getPaletteColor(color string) string {
 	return "FF" + strings.Replace(strings.ToUpper(color), "#", "", -1)
 }
+
+// themeReader provides a function to get the pointer to the xl/theme/theme1.xml
+// structure after deserialization.
+func (f *File) themeReader() *xlsxTheme {
+	var theme xlsxTheme
+	_ = xml.Unmarshal([]byte(f.readXML("xl/theme/theme1.xml")), &theme)
+	return &theme
+}
+
+// ThemeColor applied the color with tint value.
+func ThemeColor(baseColor string, tint float64) string {
+	if tint == 0 {
+		return "FF" + baseColor
+	}
+	r, _ := strconv.ParseInt(baseColor[0:2], 16, 64)
+	g, _ := strconv.ParseInt(baseColor[2:4], 16, 64)
+	b, _ := strconv.ParseInt(baseColor[4:6], 16, 64)
+	h, s, l := RGBToHSL(uint8(r), uint8(g), uint8(b))
+	if tint < 0 {
+		l *= (1 + tint)
+	} else {
+		l = l*(1-tint) + (1 - (1 - tint))
+	}
+	br, bg, bb := HSLToRGB(h, s, l)
+	return fmt.Sprintf("FF%02X%02X%02X", br, bg, bb)
+}
--- a/styles_test.go
+++ b/styles_test.go
@ -0,0 +1,134 @@
+package excelize
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSetConditionalFormat(t *testing.T) {
+	cases := []struct {
+		label  string
+		format string
+		rules  []*xlsxCfRule
+	}{{
+		label: "3_color_scale",
+		format: `[{
+			"type":"3_color_scale",
+			"criteria":"=",
+			"min_type":"num",
+			"mid_type":"num",
+			"max_type":"num",
+			"min_value": "-10",
+			"mid_value": "0",
+			"max_value": "10",
+			"min_color":"ff0000",
+			"mid_color":"00ff00",
+			"max_color":"0000ff"
+		}]`,
+		rules: []*xlsxCfRule{{
+			Priority: 1,
+			Type:     "colorScale",
+			ColorScale: &xlsxColorScale{
+				Cfvo: []*xlsxCfvo{{
+					Type: "num",
+					Val:  "-10",
+				}, {
+					Type: "num",
+					Val:  "0",
+				}, {
+					Type: "num",
+					Val:  "10",
+				}},
+				Color: []*xlsxColor{{
+					RGB: "FFFF0000",
+				}, {
+					RGB: "FF00FF00",
+				}, {
+					RGB: "FF0000FF",
+				}},
+			},
+		}},
+	}, {
+		label: "3_color_scale default min/mid/max",
+		format: `[{
+			"type":"3_color_scale",
+			"criteria":"=",
+			"min_type":"num",
+			"mid_type":"num",
+			"max_type":"num",
+			"min_color":"ff0000",
+			"mid_color":"00ff00",
+			"max_color":"0000ff"
+		}]`,
+		rules: []*xlsxCfRule{{
+			Priority: 1,
+			Type:     "colorScale",
+			ColorScale: &xlsxColorScale{
+				Cfvo: []*xlsxCfvo{{
+					Type: "num",
+					Val:  "0",
+				}, {
+					Type: "num",
+					Val:  "50",
+				}, {
+					Type: "num",
+					Val:  "0",
+				}},
+				Color: []*xlsxColor{{
+					RGB: "FFFF0000",
+				}, {
+					RGB: "FF00FF00",
+				}, {
+					RGB: "FF0000FF",
+				}},
+			},
+		}},
+	}, {
+		label: "2_color_scale default min/max",
+		format: `[{
+			"type":"2_color_scale",
+			"criteria":"=",
+			"min_type":"num",
+			"max_type":"num",
+			"min_color":"ff0000",
+			"max_color":"0000ff"
+		}]`,
+		rules: []*xlsxCfRule{{
+			Priority: 1,
+			Type:     "colorScale",
+			ColorScale: &xlsxColorScale{
+				Cfvo: []*xlsxCfvo{{
+					Type: "num",
+					Val:  "0",
+				}, {
+					Type: "num",
+					Val:  "0",
+				}},
+				Color: []*xlsxColor{{
+					RGB: "FFFF0000",
+				}, {
+					RGB: "FF0000FF",
+				}},
+			},
+		}},
+	}}
+
+	for _, testCase := range cases {
+		xl := NewFile()
+		const sheet = "Sheet1"
+		const cellRange = "A1:A1"
+
+		err := xl.SetConditionalFormat(sheet, cellRange, testCase.format)
+		if err != nil {
+			t.Fatalf("%s", err)
+		}
+
+		xlsx := xl.workSheetReader(sheet)
+		cf := xlsx.ConditionalFormatting
+		assert.Len(t, cf, 1, testCase.label)
+		assert.Len(t, cf[0].CfRule, 1, testCase.label)
+		assert.Equal(t, cellRange, cf[0].SQRef, testCase.label)
+		assert.EqualValues(t, testCase.rules, cf[0].CfRule, testCase.label)
+	}
+}
--- a/table.go
+++ b/table.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import (
@ -9,14 +18,14 @@ import (
 	"strings"
 )

-// parseFormatTableSet provides function to parse the format settings of the
+// parseFormatTableSet provides a function to parse the format settings of the
 // table with default value.
 func parseFormatTableSet(formatSet string) (*formatTable, error) {
 	format := formatTable{
 		TableStyle:     "",
 		ShowRowStripes: true,
 	}
-	err := json.Unmarshal([]byte(formatSet), &format)
+	err := json.Unmarshal(parseFormatSet(formatSet), &format)
 	return &format, err
 }

@ -75,8 +84,8 @@ func (f *File) AddTable(sheet, hcell, vcell, format string) error {
 	return err
 }

-// countTables provides function to get table files count storage in the folder
-// xl/tables.
+// countTables provides a function to get table files count storage in the
+// folder xl/tables.
 func (f *File) countTables() int {
 	count := 0
 	for k := range f.XLSX {
@ -87,7 +96,7 @@ func (f *File) countTables() int {
 	return count
 }

-// addSheetTable provides function to add tablePart element to
+// addSheetTable provides a function to add tablePart element to
 // xl/worksheets/sheet%d.xml by given worksheet name and relationship index.
 func (f *File) addSheetTable(sheet string, rID int) {
 	xlsx := f.workSheetReader(sheet)
@ -101,8 +110,8 @@ func (f *File) addSheetTable(sheet string, rID int) {
 	xlsx.TableParts.TableParts = append(xlsx.TableParts.TableParts, table)
 }

-// addTable provides function to add table by given worksheet name, coordinate
-// area and format set.
+// addTable provides a function to add table by given worksheet name,
+// coordinate area and format set.
 func (f *File) addTable(sheet, tableXML string, hxAxis, hyAxis, vxAxis, vyAxis, i int, formatSet *formatTable) {
 	// Correct the minimum number of rows, the table at least two lines.
 	if hyAxis == vyAxis {
@ -157,7 +166,7 @@ func (f *File) addTable(sheet, tableXML string, hxAxis, hyAxis, vxAxis, vyAxis,
 	f.saveFileList(tableXML, table)
 }

-// parseAutoFilterSet provides function to parse the settings of the auto
+// parseAutoFilterSet provides a function to parse the settings of the auto
 // filter.
 func parseAutoFilterSet(formatSet string) (*formatAutoFilter, error) {
 	format := formatAutoFilter{}
@ -264,7 +273,7 @@ func (f *File) AutoFilter(sheet, hcell, vcell, format string) error {
 	return f.autoFilter(sheet, ref, refRange, hxAxis, formatSet)
 }

-// autoFilter provides function to extract the tokens from the filter
+// autoFilter provides a function to extract the tokens from the filter
 // expression. The tokens are mainly non-whitespace groups.
 func (f *File) autoFilter(sheet, ref string, refRange, hxAxis int, formatSet *formatAutoFilter) error {
 	xlsx := f.workSheetReader(sheet)
@ -282,7 +291,7 @@ func (f *File) autoFilter(sheet, ref string, refRange, hxAxis int, formatSet *fo
 	col := TitleToNumber(formatSet.Column)
 	offset := col - hxAxis
 	if offset < 0 || offset > refRange {
-		return fmt.Errorf("Incorrect index of column '%s'", formatSet.Column)
+		return fmt.Errorf("incorrect index of column '%s'", formatSet.Column)
 	}
 	filter.FilterColumn = &xlsxFilterColumn{
 		ColID: offset,
@ -290,7 +299,7 @@ func (f *File) autoFilter(sheet, ref string, refRange, hxAxis int, formatSet *fo
 	re := regexp.MustCompile(`"(?:[^"]|"")*"|\S+`)
 	token := re.FindAllString(formatSet.Expression, -1)
 	if len(token) != 3 && len(token) != 7 {
-		return fmt.Errorf("Incorrect number of tokens in criteria '%s'", formatSet.Expression)
+		return fmt.Errorf("incorrect number of tokens in criteria '%s'", formatSet.Expression)
 	}
 	expressions, tokens, err := f.parseFilterExpression(formatSet.Expression, token)
 	if err != nil {
@ -301,8 +310,8 @@ func (f *File) autoFilter(sheet, ref string, refRange, hxAxis int, formatSet *fo
 	return nil
 }

-// writeAutoFilter provides function to check for single or double custom filters
-// as default filters and handle them accordingly.
+// writeAutoFilter provides a function to check for single or double custom
+// filters as default filters and handle them accordingly.
 func (f *File) writeAutoFilter(filter *xlsxAutoFilter, exp []int, tokens []string) {
 	if len(exp) == 1 && exp[0] == 2 {
 		// Single equality.
@ -329,7 +338,7 @@ func (f *File) writeAutoFilter(filter *xlsxAutoFilter, exp []int, tokens []strin
 	}
 }

-// writeCustomFilter provides function to write the <customFilter> element.
+// writeCustomFilter provides a function to write the <customFilter> element.
 func (f *File) writeCustomFilter(filter *xlsxAutoFilter, operator int, val string) {
 	operators := map[int]string{
 		1:  "lessThan",
@ -353,8 +362,9 @@ func (f *File) writeCustomFilter(filter *xlsxAutoFilter, operator int, val strin
 	}
 }

-// parseFilterExpression provides function to converts the tokens of a possibly
-// conditional expression into 1 or 2 sub expressions for further parsing.
+// parseFilterExpression provides a function to converts the tokens of a
+// possibly conditional expression into 1 or 2 sub expressions for further
+// parsing.
 //
 // Examples:
 //
@ -394,7 +404,7 @@ func (f *File) parseFilterExpression(expression string, tokens []string) ([]int,
 	return expressions, t, nil
 }

-// parseFilterTokens provides function to parse the 3 tokens of a filter
+// parseFilterTokens provides a function to parse the 3 tokens of a filter
 // expression and return the operator and token.
 func (f *File) parseFilterTokens(expression string, tokens []string) ([]int, string, error) {
 	operators := map[string]int{
@ -414,7 +424,7 @@ func (f *File) parseFilterTokens(expression string, tokens []string) ([]int, str
 	operator, ok := operators[strings.ToLower(tokens[1])]
 	if !ok {
 		// Convert the operator from a number to a descriptive string.
-		return []int{}, "", fmt.Errorf("Unknown operator: %s", tokens[1])
+		return []int{}, "", fmt.Errorf("unknown operator: %s", tokens[1])
 	}
 	token := tokens[2]
 	// Special handling for Blanks/NonBlanks.
@ -422,7 +432,7 @@ func (f *File) parseFilterTokens(expression string, tokens []string) ([]int, str
 	if re {
 		// Only allow Equals or NotEqual in this context.
 		if operator != 2 && operator != 5 {
-			return []int{operator}, token, fmt.Errorf("The operator '%s' in expression '%s' is not valid in relation to Blanks/NonBlanks'", tokens[1], expression)
+			return []int{operator}, token, fmt.Errorf("the operator '%s' in expression '%s' is not valid in relation to Blanks/NonBlanks'", tokens[1], expression)
 		}
 		token = strings.ToLower(token)
 		// The operator should always be 2 (=) to flag a "simple" equality in
--- a/templates.go
+++ b/templates.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+//
 // This file contains default templates for XML files we don't yet populated
 // based on content.

--- a/vmlDrawing.go
+++ b/vmlDrawing.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import "encoding/xml"
--- a/xmlChart.go
+++ b/xmlChart.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import "encoding/xml"
--- a/xmlComments.go
+++ b/xmlComments.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import "encoding/xml"
@ -53,3 +62,11 @@ type formatComment struct {
 	Author string `json:"author"`
 	Text   string `json:"text"`
 }
+
+// Comment directly maps the comment information.
+type Comment struct {
+	Author   string `json:"author"`
+	AuthorID int    `json:"author_id"`
+	Ref      string `json:"ref"`
+	Text     string `json:"text"`
+}
--- a/xmlContentTypes.go
+++ b/xmlContentTypes.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import "encoding/xml"
--- a/xmlDecodeDrawing.go
+++ b/xmlDecodeDrawing.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import "encoding/xml"
--- a/xmlDrawing.go
+++ b/xmlDrawing.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import "encoding/xml"
--- a/xmlSharedStrings.go
+++ b/xmlSharedStrings.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import "encoding/xml"
--- a/xmlStyles.go
+++ b/xmlStyles.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import "encoding/xml"
--- a/xmlTable.go
+++ b/xmlTable.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import "encoding/xml"
--- a/xmlTheme.go
+++ b/xmlTheme.go
@ -0,0 +1,149 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
+package excelize
+
+import "encoding/xml"
+
+// xlsxTheme directly maps the theme element in the namespace
+// http://schemas.openxmlformats.org/drawingml/2006/main
+type xlsxTheme struct {
+	ThemeElements     xlsxThemeElements     `xml:"themeElements"`
+	ObjectDefaults    xlsxObjectDefaults    `xml:"objectDefaults"`
+	ExtraClrSchemeLst xlsxExtraClrSchemeLst `xml:"extraClrSchemeLst"`
+	ExtLst            *xlsxExtLst           `xml:"extLst"`
+}
+
+// objectDefaults element allows for the definition of default shape, line,
+// and textbox formatting properties. An application can use this information
+// to format a shape (or text) initially on insertion into a document.
+type xlsxObjectDefaults struct {
+	ObjectDefaults string `xml:",innerxml"`
+}
+
+// xlsxExtraClrSchemeLst element is a container for the list of extra color
+// schemes present in a document.
+type xlsxExtraClrSchemeLst struct {
+	ExtraClrSchemeLst string `xml:",innerxml"`
+}
+
+// xlsxThemeElements directly maps the element defines the theme formatting
+// options for the theme and is the workhorse of the theme. This is where the
+// bulk of the shared theme information is contained and used by a document.
+// This element contains the color scheme, font scheme, and format scheme
+// elements which define the different formatting aspects of what a theme
+// defines.
+type xlsxThemeElements struct {
+	ClrScheme  xlsxClrScheme  `xml:"clrScheme"`
+	FontScheme xlsxFontScheme `xml:"fontScheme"`
+	FmtScheme  xlsxFmtScheme  `xml:"fmtScheme"`
+}
+
+// xlsxClrScheme element specifies the theme color, stored in the document's
+// Theme part to which the value of this theme color shall be mapped. This
+// mapping enables multiple theme colors to be chained together.
+type xlsxClrScheme struct {
+	Name     string            `xml:"name,attr"`
+	Children []xlsxClrSchemeEl `xml:",any"`
+}
+
+// xlsxFontScheme element defines the font scheme within the theme. The font
+// scheme consists of a pair of major and minor fonts for which to use in a
+// document. The major font corresponds well with the heading areas of a
+// document, and the minor font corresponds well with the normal text or
+// paragraph areas.
+type xlsxFontScheme struct {
+	Name      string        `xml:"name,attr"`
+	MajorFont xlsxMajorFont `xml:"majorFont"`
+	MinorFont xlsxMinorFont `xml:"minorFont"`
+	ExtLst    *xlsxExtLst   `xml:"extLst"`
+}
+
+// xlsxMajorFont element defines the set of major fonts which are to be used
+// under different languages or locals.
+type xlsxMajorFont struct {
+	Children []xlsxFontSchemeEl `xml:",any"`
+}
+
+// xlsxMinorFont element defines the set of minor fonts that are to be used
+// under different languages or locals.
+type xlsxMinorFont struct {
+	Children []xlsxFontSchemeEl `xml:",any"`
+}
+
+// xlsxFmtScheme element contains the background fill styles, effect styles,
+// fill styles, and line styles which define the style matrix for a theme. The
+// style matrix consists of subtle, moderate, and intense fills, lines, and
+// effects. The background fills are not generally thought of to directly be
+// associated with the matrix, but do play a role in the style of the overall
+// document. Usually, a given object chooses a single line style, a single
+// fill style, and a single effect style in order to define the overall final
+// look of the object.
+type xlsxFmtScheme struct {
+	Name           string             `xml:"name,attr"`
+	FillStyleLst   xlsxFillStyleLst   `xml:"fillStyleLst"`
+	LnStyleLst     xlsxLnStyleLst     `xml:"lnStyleLst"`
+	EffectStyleLst xlsxEffectStyleLst `xml:"effectStyleLst"`
+	BgFillStyleLst xlsxBgFillStyleLst `xml:"bgFillStyleLst"`
+}
+
+// xlsxFillStyleLst element defines a set of three fill styles that are used
+// within a theme. The three fill styles are arranged in order from subtle to
+// moderate to intense.
+type xlsxFillStyleLst struct {
+	FillStyleLst string `xml:",innerxml"`
+}
+
+// xlsxLnStyleLst element defines a list of three line styles for use within a
+// theme. The three line styles are arranged in order from subtle to moderate
+// to intense versions of lines. This list makes up part of the style matrix.
+type xlsxLnStyleLst struct {
+	LnStyleLst string `xml:",innerxml"`
+}
+
+// xlsxEffectStyleLst element defines a set of three effect styles that create
+// the effect style list for a theme. The effect styles are arranged in order
+// of subtle to moderate to intense.
+type xlsxEffectStyleLst struct {
+	EffectStyleLst string `xml:",innerxml"`
+}
+
+// xlsxBgFillStyleLst  element defines a list of background fills that are
+// used within a theme. The background fills consist of three fills, arranged
+// in order from subtle to moderate to intense.
+type xlsxBgFillStyleLst struct {
+	BgFillStyleLst string `xml:",innerxml"`
+}
+
+// xlsxClrScheme maps to children of the clrScheme element in the namespace
+// http://schemas.openxmlformats.org/drawingml/2006/main - currently I have
+// not checked it for completeness - it does as much as I need.
+type xlsxClrSchemeEl struct {
+	XMLName xml.Name
+	SysClr  *xlsxSysClr    `xml:"sysClr"`
+	SrgbClr *attrValString `xml:"srgbClr"`
+}
+
+// xlsxFontSchemeEl directly maps the major and minor font of the style's font
+// scheme.
+type xlsxFontSchemeEl struct {
+	XMLName     xml.Name
+	Script      string `xml:"script,attr,omitempty"`
+	Typeface    string `xml:"typeface,attr"`
+	Panose      string `xml:"panose,attr,omitempty"`
+	PitchFamily string `xml:"pitchFamily,attr,omitempty"`
+	Charset     string `xml:"charset,attr,omitempty"`
+}
+
+// xlsxSysClr element specifies a color bound to predefined operating system
+// elements.
+type xlsxSysClr struct {
+	Val     string `xml:"val,attr"`
+	LastClr string `xml:"lastClr,attr"`
+}
--- a/xmlWorkbook.go
+++ b/xmlWorkbook.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import "encoding/xml"
--- a/xmlWorksheet.go
+++ b/xmlWorksheet.go
@ -1,3 +1,12 @@
+// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
+// this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+//
+// Package excelize providing a set of functions that allow you to write to
+// and read from XLSX files. Support reads and writes XLSX file generated by
+// Microsoft Excel™ 2007 and later. Support save file without losing original
+// charts of XLSX. This library needs Go version 1.8 or later.
+
 package excelize

 import "encoding/xml"
@ -18,7 +27,7 @@ type xlsxWorksheet struct {
 	MergeCells            *xlsxMergeCells              `xml:"mergeCells"`
 	PhoneticPr            *xlsxPhoneticPr              `xml:"phoneticPr"`
 	ConditionalFormatting []*xlsxConditionalFormatting `xml:"conditionalFormatting"`
-	DataValidations       *xlsxDataValidations         `xml:"dataValidations"`
+	DataValidations       *xlsxDataValidations         `xml:"dataValidations,omitempty"`
 	Hyperlinks            *xlsxHyperlinks              `xml:"hyperlinks"`
 	PrintOptions          *xlsxPrintOptions            `xml:"printOptions"`
 	PageMargins           *xlsxPageMargins             `xml:"pageMargins"`
@ -294,11 +303,30 @@ type xlsxMergeCells struct {
 // xlsxDataValidations expresses all data validation information for cells in a
 // sheet which have data validation features applied.
 type xlsxDataValidations struct {
-	Count          int    `xml:"count,attr,omitempty"`
-	DisablePrompts bool   `xml:"disablePrompts,attr,omitempty"`
-	XWindow        int    `xml:"xWindow,attr,omitempty"`
-	YWindow        int    `xml:"yWindow,attr,omitempty"`
-	DataValidation string `xml:",innerxml"`
+	Count          int               `xml:"count,attr,omitempty"`
+	DisablePrompts bool              `xml:"disablePrompts,attr,omitempty"`
+	XWindow        int               `xml:"xWindow,attr,omitempty"`
+	YWindow        int               `xml:"yWindow,attr,omitempty"`
+	DataValidation []*DataValidation `xml:"dataValidation"`
+}
+
+// DataValidation directly maps the a single item of data validation defined
+// on a range of the worksheet.
+type DataValidation struct {
+	AllowBlank       bool    `xml:"allowBlank,attr"`
+	Error            *string `xml:"error,attr"`
+	ErrorStyle       *string `xml:"errorStyle,attr"`
+	ErrorTitle       *string `xml:"errorTitle,attr"`
+	Operator         string  `xml:"operator,attr"`
+	Prompt           *string `xml:"prompt,attr"`
+	PromptTitle      *string `xml:"promptTitle"`
+	ShowDropDown     bool    `xml:"showDropDown,attr"`
+	ShowErrorMessage bool    `xml:"showErrorMessage,attr"`
+	ShowInputMessage bool    `xml:"showInputMessage,attr"`
+	Sqref            string  `xml:"sqref,attr"`
+	Type             string  `xml:"type,attr"`
+	Formula1         string  `xml:"formula1"`
+	Formula2         string  `xml:"formula2"`
 }

 // xlsxC directly maps the c element in the namespace
@ -446,7 +474,7 @@ type xlsxIconSet struct {
 type xlsxCfvo struct {
 	Gte    bool        `xml:"gte,attr,omitempty"`
 	Type   string      `xml:"type,attr,omitempty"`
-	Val    int         `xml:"val,attr"`
+	Val    string      `xml:"val,attr"`
 	ExtLst *xlsxExtLst `xml:"extLst"`
 }