一款html5 canvas实现的图片玻璃碎片特效

<img src="city_copy.jpg" id="src_img" class="hidden"> 
<div id="container" style="-webkit-perspective: 500px;"> 
<div> 
<script src="delaunay.js"></script> 
<script src="TweenMax.min.js"></script>

// canvas settings 
var imageWidth = 768, 
imageHeight = 485; 
var vertices = [], 
indices, 
boxes = []; 
var image, 
fragments = [], 
container = document.getElementById('container'); 
window.onload = function () { 
image = document.getElementById('src_img'); 
triangulate(); 
makeBoxes(); 
makeFragments(); 
}; 
function triangulate() { 
var x, 
y, 
dx = imageWidth / 8, 
dy = imageHeight / 8, 
offset = 0.5; 
for (var i = 0; i <= imageWidth; i += dx) { 
for (var j = 0; j <= imageHeight; j += dy) { 
if (i && (i !== imageWidth)) x = i + randomRange(-dx * offset, dx * offset); 
else x = i; 
if (j && (j !== imageHeight)) y = j + randomRange(-dy * offset, dy * offset); 
else y = j; 
vertices.push([x, y]); 
} 
} 
indices = Delaunay.triangulate(vertices); 
} 
function makeBoxes() { 
var p0, p1, p2, 
xMin, xMax, 
yMin, yMax; 
for (var i = 0; i < indices.length; i += 3) { 
p0 = vertices[indices[i + 0]]; 
p1 = vertices[indices[i + 1]]; 
p2 = vertices[indices[i + 2]]; 
xMin = Math.min(p0[0], p1[0], p2[0]); 
xMax = Math.max(p0[0], p1[0], p2[0]); 
yMin = Math.min(p0[1], p1[1], p2[1]); 
yMax = Math.max(p0[1], p1[1], p2[1]); 
boxes.push({ 
x: xMin, 
y: yMin, 
w: xMax - xMin, 
h: yMax - yMin 
}); 
} 
} 
function makeFragments() { 
var p0, p1, p2, 
box, 
fragment; 
TweenMax.set(container, { perspective: 500 }); 
var tl0 = new TimelineMax({ repeat: -1 }); 
for (var i = 0; i < indices.length; i += 3) { 
p0 = vertices[indices[i + 0]]; 
p1 = vertices[indices[i + 1]]; 
p2 = vertices[indices[i + 2]]; 
box = boxes[i / 3]; 
fragment = new Fragment(p0, p1, p2, box); 
var rx = randomRange(30, 60) * ((i % 2) ? 1 : -1); 
var ry = randomRange(30, 60) * ((i % 2) ? -1 : 1); 
var tl1 = new TimelineMax(); 
TweenMax.set(fragment.canvas, { 
y: box.y - 1000 
}); 
tl1.to(fragment.canvas, randomRange(0.9, 1.1), { 
y: box.y, 
ease: Back.easeOut 
}); 
tl1.to(fragment.canvas, 0.5, { 
z: -100, 
ease: Cubic.easeIn, 
delay: 0.4 
}); 
tl1.to(fragment.canvas, randomRange(1, 1.2), { 
rotationX: rx, 
rotationY: ry, 
z: 250, 
alpha: 0, 
ease: Cubic.easeOut 
}); 
tl0.insert(tl1); 
fragments.push(fragment); 
container.appendChild(fragment.canvas); 
} 
} 
function randomRange(min, max) { 
return min + (max - min) * Math.random(); 
} 
Fragment = function (v0, v1, v2, box) { 
this.v0 = v0; 
this.v1 = v1; 
this.v2 = v2; 
this.box = box; 
this.canvas = document.createElement('canvas'); 
this.canvas.width = this.box.w; 
this.canvas.height = this.box.h; 
this.canvas.style.width = this.box.w + 'px'; 
this.canvas.style.height = this.box.h + 'px'; 
this.ctx = this.canvas.getContext('2d'); 
TweenMax.set(this.canvas, { 
x: this.box.x, 
y: this.box.y 
}); 
this.ctx.translate(-this.box.x, -this.box.y); 
this.ctx.beginPath(); 
this.ctx.moveTo(this.v0[0], this.v0[1]); 
this.ctx.lineTo(this.v1[0], this.v1[1]); 
this.ctx.lineTo(this.v2[0], this.v2[1]); 
this.ctx.closePath(); 
this.ctx.clip(); 
this.ctx.drawImage(image, 0, 0); 
}; //@ sourceURL=pen.js