142 lines
3.5 KiB
Go
142 lines
3.5 KiB
Go
/*
|
|
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
|
|
}
|