<!DOCTYPE html>
<title>PathKit (Skia's Geometry + asm.js)</title>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
svg, canvas {
border: 1px dashed #AAA;
}
canvas {
width: 200px;
height: 200px;
}
canvas.big {
width: 300px;
height: 300px;
}
</style>
<h2> Can output to an SVG Path, a Canvas, or a Path2D object </h2>
<svg id=svg1 xmlns='http://www.w3.org/2000/svg' width=200 height=200></svg>
<canvas id=canvas1></canvas>
<canvas id=canvas2></canvas>
<h2> Interact with NewPath() just like a Path2D Object </h2>
<canvas class=big id=canvas3></canvas>
<canvas class=big id=canvas4></canvas>
<h2> Has various Path Effects </h2>
<canvas class=big id=canvas5></canvas>
<canvas class=big id=canvas6></canvas>
<canvas class=big id=canvas7></canvas>
<canvas class=big id=canvas8></canvas>
<canvas class=big id=canvas9></canvas>
<canvas class=big id=canvas10></canvas>
<canvas class=big id=canvas11></canvas>
<canvas class=big id=canvasTransform></canvas>
<h2> Supports fill-rules of nonzero and evenodd </h2>
<svg id=svg2 xmlns='http://www.w3.org/2000/svg' width=200 height=200></svg>
<svg id=svg3 xmlns='http://www.w3.org/2000/svg' width=200 height=200></svg>
<h2> Solves Cubics for Y given X </h2>
<canvas class=big id=cubics></canvas>
<script type="text/javascript" src="/node_modules/pathkit-asmjs/bin/pathkit.js"></script>
<script type="text/javascript" charset="utf-8">
PathKitInit({
locateFile: (file) => '/node_modules/pathkit-asmjs/bin/'+file,
}).ready().then((PathKit) => {
window.PathKit = PathKit;
OutputsExample(PathKit);
Path2DExample(PathKit);
PathEffectsExample(PathKit);
MatrixTransformExample(PathKit);
FilledSVGExample(PathKit);
CubicSolverExample(PathKit);
});
function setCanvasSize(ctx, width, height) {
ctx.canvas.width = width;
ctx.canvas.height = height;
}
function OutputsExample(PathKit) {
let firstPath = PathKit.FromSVGString('M11.99 2C6.47 2 2 6.48 2 12s4.47 10 9.99 10C17.52 22 22 17.52 22 12S17.52 2 11.99 2zM12 20c-4.42 0-8-3.58-8-8s3.58-8 8-8 8 3.58 8 8-3.58 8-8 8zm.5-13H11v6l5.25 3.15.75-1.23-4.5-2.67z');
let secondPath = PathKit.NewPath();
// Acts somewhat like the Canvas API, except can be chained
secondPath.moveTo(1, 1)
.lineTo(20, 1)
.lineTo(10, 30)
.closePath();
// Join the two paths together (mutating firstPath in the process)
firstPath.op(secondPath, PathKit.PathOp.INTERSECT);
let simpleStr = firstPath.toSVGString();
let newSVG = document.createElementNS('http://www.w3.org/2000/svg', 'path');
newSVG.setAttribute('stroke', 'rgb(0,0,200)');
newSVG.setAttribute('fill', 'white');
newSVG.setAttribute('transform', 'scale(8,8)');
newSVG.setAttribute('d', simpleStr);
document.getElementById('svg1').appendChild(newSVG);
// Draw directly to Canvas
let ctx = document.getElementById('canvas1').getContext('2d');
setCanvasSize(ctx, 200, 200);
ctx.strokeStyle = 'green';
ctx.fillStyle = 'white';
ctx.scale(8, 8);
ctx.beginPath();
firstPath.toCanvas(ctx);
ctx.stroke();
// create Path2D object and use it in a Canvas.
let path2D = firstPath.toPath2D();
ctx = document.getElementById('canvas2').getContext('2d');
setCanvasSize(ctx, 200, 200);
ctx.canvas.width = 200
ctx.scale(8, 8);
ctx.fillStyle = 'purple';
ctx.strokeStyle = 'orange';
ctx.fill(path2D);
ctx.stroke(path2D);
// clean up memory and call destructors in the c++ code (if any).
// See http://kripken.github.io/emscripten-site/docs/porting/connecting_cpp_and_javascript/embind.html?highlight=memory#memory-management
firstPath.delete();
secondPath.delete();
}
function Path2DExample(PathKit) {
let objs = [new Path2D(), PathKit.NewPath(), new Path2D(), PathKit.NewPath()];
let canvases = [
document.getElementById('canvas3').getContext('2d'),
document.getElementById('canvas4').getContext('2d')
];
for (i = 0; i <= 1; i++) {
let path = objs[i];
path.moveTo(20, 5);
path.lineTo(30, 20);
path.lineTo(40, 10);
path.lineTo(50, 20);
path.lineTo(60, 0);
path.lineTo(20, 5);
path.moveTo(20, 80);
path.bezierCurveTo(90, 10, 160, 150, 190, 10);
path.moveTo(36, 148);
path.quadraticCurveTo(66, 188, 120, 136);
path.lineTo(36, 148);
path.rect(5, 170, 20, 20);
path.moveTo(150, 180);
path.arcTo(150, 100, 50, 200, 20);
path.lineTo(160, 160);
path.moveTo(20, 120);
path.arc(20, 120, 18, 0, 1.75 * Math.PI);
path.lineTo(20, 120);
let secondPath = objs[i+2];
secondPath.ellipse(130, 25, 30, 10, -1*Math.PI/8, Math.PI/6, 1.5*Math.PI, false);
path.addPath(secondPath);
let m = document.createElementNS('http://www.w3.org/2000/svg', 'svg').createSVGMatrix();
m.a = 1; m.b = 0;
m.c = 0; m.d = 1;
m.e = 0; m.f = 20.5;
path.addPath(secondPath, m);
// With PathKit, one can also just provide the 6 params as floats, to avoid
// the overhead of making an SVGMatrix
// path.addPath(secondPath, 1, 0, 0, 1, 0, 20.5);
canvasCtx = canvases[i];
canvasCtx.fillStyle = 'blue';
setCanvasSize(canvasCtx, 300, 300);
canvasCtx.scale(1.5, 1.5);
if (path.toPath2D) {
canvasCtx.stroke(path.toPath2D());
} else {
canvasCtx.stroke(path);
}
}
objs[1].delete();
}
// see https://fiddle.skia.org/c/@discrete_path
function drawStar(path) {
let R = 115.2, C = 128.0;
path.moveTo(C + R + 22, C);
for (let i = 1; i < 8; i++) {
let a = 2.6927937 * i;
path.lineTo(C + R * Math.cos(a) + 22, C + R * Math.sin(a));
}
path.closePath();
return path;
}
function PathEffectsExample(PathKit) {
let effects = [
// no-op
(path) => path,
// dash
(path, counter) => path.dash(10, 3, counter/5),
// trim (takes optional 3rd param for returning the trimmed part
// or the complement)
(path, counter) => path.trim((counter/100) % 1, 0.8, false),
// simplify
(path) => path.simplify(),
// stroke
(path, counter) => path.stroke({
width: 10 * (Math.sin(counter/30) + 1),
join: PathKit.StrokeJoin.BEVEL,
cap: PathKit.StrokeCap.BUTT,
miter_limit: 1,
}),
// "offset effect", that is, making a border around the shape.
(path, counter) => {
let orig = path.copy();
path.stroke({
width: 10 + (counter / 4) % 50,
join: PathKit.StrokeJoin.ROUND,
cap: PathKit.StrokeCap.SQUARE,
})
.op(orig, PathKit.PathOp.DIFFERENCE);
orig.delete();
},
(path, counter) => {
let simplified = path.simplify().copy();
path.stroke({
width: 2 + (counter / 2) % 100,
join: PathKit.StrokeJoin.BEVEL,
cap: PathKit.StrokeCap.BUTT,
})
.op(simplified, PathKit.PathOp.REVERSE_DIFFERENCE);
simplified.delete();
}
];
let names = ["(plain)", "Dash", "Trim", "Simplify", "Stroke", "Grow", "Shrink"];
let counter = 0;
function frame() {
counter++;
for (let i = 0; i < effects.length; i++) {
let path = PathKit.NewPath();
drawStar(path);
// The transforms apply directly to the path.
effects[i](path, counter);
let ctx = document.getElementById(`canvas${i+5}`).getContext('2d');
setCanvasSize(ctx, 300, 300);
ctx.strokeStyle = '#3c597a';
ctx.fillStyle = '#3c597a';
if (i >=4 ) {
ctx.fill(path.toPath2D(), path.getFillTypeString());
} else {
ctx.stroke(path.toPath2D());
}
ctx.font = '42px monospace';
let x = 150-ctx.measureText(names[i]).width/2;
ctx.strokeText(names[i], x, 290);
path.delete();
}
window.requestAnimationFrame(frame);
}
window.requestAnimationFrame(frame);
}
function MatrixTransformExample(PathKit) {
// Creates an animated star that twists and moves.
let ctx = document.getElementById('canvasTransform').getContext('2d');
setCanvasSize(ctx, 300, 300);
ctx.strokeStyle = '#3c597a';
let path = drawStar(PathKit.NewPath());
// TODO(kjlubick): Perhaps expose some matrix helper functions to allow
// clients to build their own matrices like this?
// These matrices represent a 2 degree rotation and a 1% scale factor.
let scaleUp = [1.0094, -0.0352, 3.1041,
0.0352, 1.0094, -6.4885,
0 , 0 , 1];
let scaleDown = [ 0.9895, 0.0346, -2.8473,
-0.0346, 0.9895, 6.5276,
0 , 0 , 1];
let i = 0;
function frame(){
i++;
if (Math.round(i/100) % 2) {
path.transform(scaleDown);
} else {
path.transform(scaleUp);
}
ctx.clearRect(0, 0, 300, 300);
ctx.stroke(path.toPath2D());
ctx.font = '42px monospace';
let x = 150-ctx.measureText('Transform').width/2;
ctx.strokeText('Transform', x, 290);
window.requestAnimationFrame(frame);
}
window.requestAnimationFrame(frame);
}
function FilledSVGExample(PathKit) {
let innerRect = PathKit.NewPath();
innerRect.rect(80, 100, 40, 40);
let outerRect = PathKit.NewPath();
outerRect.rect(50, 10, 100, 100)
.op(innerRect, PathKit.PathOp.XOR);
let str = outerRect.toSVGString();
let diffSVG = document.createElementNS('http://www.w3.org/2000/svg', 'path');
diffSVG.setAttribute('stroke', 'red');
diffSVG.setAttribute('fill', 'black');
// force fill-rule to nonzero to demonstrate difference
diffSVG.setAttribute('fill-rule', 'nonzero');
diffSVG.setAttribute('d', str);
document.getElementById('svg2').appendChild(diffSVG);
let unionSVG = document.createElementNS('http://www.w3.org/2000/svg', 'path');
unionSVG.setAttribute('stroke', 'red');
unionSVG.setAttribute('fill', 'black');
// ask what the path thinks fill-rule should be ('evenodd')
// SVG and Canvas both use the same keys ('nonzero' and 'evenodd') and both
// default to 'nonzero', so one call supports both.
unionSVG.setAttribute('fill-rule', outerRect.getFillTypeString());
unionSVG.setAttribute('d', str);
document.getElementById('svg3').appendChild(unionSVG);
outerRect.delete();
innerRect.delete();
}
function CubicSolverExample(PathKit) {
let ctx = document.getElementById('cubics').getContext('2d');
setCanvasSize(ctx, 300, 300);
// Draw lines between cp0 (0, 0) and cp1 and then cp2 and cp3 (1, 1)
// scaled up to be on a 300x300 grid instead of unit square
ctx.strokeStyle = 'black';
ctx.beginPath();
ctx.moveTo(0, 0);
ctx.lineTo(0.1 * 300, 0.5*300);
ctx.moveTo(0.5 * 300, 0.1*300);
ctx.lineTo(300, 300);
ctx.stroke();
ctx.strokeStyle = 'green';
ctx.beginPath();
for (let x = 0; x < 300; x++) {
// scale X into unit square
let y = PathKit.cubicYFromX(0.1, 0.5, 0.5, 0.1, x/300);
ctx.arc(x, y*300, 2, 0, 2*Math.PI);
}
ctx.stroke();
}
</script>