68 lines
1.5 KiB
JavaScript
68 lines
1.5 KiB
JavaScript
var ctx = document.getElementById('tutorial').getContext('2d');
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ctx.strokeStyle = "#fc0";
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ctx.lineWidth = 1.5;
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ctx.fillRect(0,0,300,300);
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// Uniform scaling
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ctx.save()
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ctx.translate(50,50);
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drawSpirograph(ctx,22,6,5); // no scaling
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ctx.translate(100,0);
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ctx.scale(0.75,0.75);
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drawSpirograph(ctx,22,6,5);
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ctx.translate(133.333,0);
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ctx.scale(0.75,0.75);
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drawSpirograph(ctx,22,6,5);
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ctx.restore();
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// Non uniform scaling (y direction)
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ctx.strokeStyle = "#0cf";
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ctx.save()
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ctx.translate(50,150);
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ctx.scale(1,0.75);
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drawSpirograph(ctx,22,6,5);
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ctx.translate(100,0);
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ctx.scale(1,0.75);
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drawSpirograph(ctx,22,6,5);
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ctx.translate(100,0);
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ctx.scale(1,0.75);
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drawSpirograph(ctx,22,6,5);
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ctx.restore();
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// Non uniform scaling (x direction)
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ctx.strokeStyle = "#cf0";
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ctx.save()
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ctx.translate(50,250);
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ctx.scale(0.75,1);
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drawSpirograph(ctx,22,6,5);
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ctx.translate(133.333,0);
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ctx.scale(0.75,1);
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drawSpirograph(ctx,22,6,5);
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ctx.translate(177.777,0);
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ctx.scale(0.75,1);
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drawSpirograph(ctx,22,6,5);
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ctx.restore();
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function drawSpirograph(ctx,R,r,O){
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var x1 = R-O;
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var y1 = 0;
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var i = 1;
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ctx.beginPath();
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ctx.moveTo(x1,y1);
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do {
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if (i>20000) break;
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var x2 = (R+r)*Math.cos(i*Math.PI/72) - (r+O)*Math.cos(((R+r)/r)*(i*Math.PI/72))
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var y2 = (R+r)*Math.sin(i*Math.PI/72) - (r+O)*Math.sin(((R+r)/r)*(i*Math.PI/72))
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ctx.lineTo(x2,y2);
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x1 = x2;
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y1 = y2;
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i++;
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} while (x2 != R-O && y2 != 0 );
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ctx.stroke();
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}
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