JavaScript+html5 canvas实现图片破碎重组动画特效

<div style="display:none"> <video id="sourcevid" autoplay="true" loop="true">  <source src="BigBuckBunny_640x360.mp4" type="video/mp4"/>  <source src="BigBuckBunny_640x360.ogv" type="video/ogg"/> </video> <canvas id="sourcecopy" width="640" height="360"></canvas></div><div><center> <div style="z-index:1;position:relative;text-align:center;font-size:16px;font-weight:bold;width:1000px;top:60px;">Click video to blow it up!</div> <canvas id="output" width="1000" height="600" onmousedown="dropBomb(event, this)" style="border: 0 none">    </canvas></center></div>

var video;var copy;var copycanvas;var draw;var TILE_WIDTH = 32;var TILE_HEIGHT = 24;var TILE_CENTER_WIDTH = 16;var TILE_CENTER_HEIGHT = 12;var SOURCERECT = {x:0, y:0, width:0, height:0};var PAINTRECT = {x:0, y:0, width:1000, height:600};function init(){ video = document.getElementById('sourcevid'); copycanvas = document.getElementById('sourcecopy'); copy = copycanvas.getContext('2d'); var outputcanvas = document.getElementById('output'); draw = outputcanvas.getContext('2d'); setInterval("processFrame()", 33);}function createTiles(){ var offsetX = TILE_CENTER_WIDTH+(PAINTRECT.width-SOURCERECT.width)/2; var offsetY = TILE_CENTER_HEIGHT+(PAINTRECT.height-SOURCERECT.height)/2; var y=0; while(y < SOURCERECT.height){ var x=0; while(x < SOURCERECT.width){  var tile = new Tile();  tile.videoX = x;  tile.videoY = y;  tile.originX = offsetX+x;  tile.originY = offsetY+y;  tile.currentX = tile.originX;  tile.currentY = tile.originY;  tiles.push(tile);  x+=TILE_WIDTH; } y+=TILE_HEIGHT; }}var RAD = Math.PI/180;var randomJump = false;var tiles = [];var debug = false;function processFrame(){ if(!isNaN(video.duration)){ if(SOURCERECT.width == 0){  SOURCERECT = {x:0,y:0,width:video.videoWidth,height:video.videoHeight};  createTiles(); } //this is to keep my sanity while developing if(randomJump){  randomJump = false;  video.currentTime = Math.random()*video.duration; } //loop if(video.currentTime == video.duration){  video.currentTime = 0; } } var debugStr = ""; //copy tiles copy.drawImage(video, 0, 0); draw.clearRect(PAINTRECT.x, PAINTRECT.y,PAINTRECT.width,PAINTRECT.height); for(var i=0; i<tiles.length; i++){ var tile = tiles[i]; if(tile.force > 0.0001){  //expand  tile.moveX *= tile.force;  tile.moveY *= tile.force;  tile.moveRotation *= tile.force;  tile.currentX += tile.moveX;  tile.currentY += tile.moveY;  tile.rotation += tile.moveRotation;  tile.rotation %= 360;  tile.force *= 0.9;  if(tile.currentX <= 0 || tile.currentX >= PAINTRECT.width){  tile.moveX *= -1;  }  if(tile.currentY <= 0 || tile.currentY >= PAINTRECT.height){  tile.moveY *= -1;  } }else if(tile.rotation != 0 || tile.currentX != tile.originX || tile.currentY != tile.originY){  //contract  var diffx = (tile.originX-tile.currentX)*0.2;  var diffy = (tile.originY-tile.currentY)*0.2;  var diffRot = (0-tile.rotation)*0.2;  if(Math.abs(diffx) < 0.5){  tile.currentX = tile.originX;  }else{  tile.currentX += diffx;  }  if(Math.abs(diffy) < 0.5){  tile.currentY = tile.originY;  }else{  tile.currentY += diffy;  }  if(Math.abs(diffRot) < 0.5){  tile.rotation = 0;  }else{  tile.rotation += diffRot;  } }else{  tile.force = 0; } draw.save(); draw.translate(tile.currentX, tile.currentY); draw.rotate(tile.rotation*RAD); draw.drawImage(copycanvas, tile.videoX, tile.videoY, TILE_WIDTH, TILE_HEIGHT, -TILE_CENTER_WIDTH, -TILE_CENTER_HEIGHT, TILE_WIDTH, TILE_HEIGHT); draw.restore(); } if(debug){ debug = false; document.getElementById('trace').innerHTML = debugStr; }}function explode(x, y){ for(var i=0; i<tiles.length; i++){ var tile = tiles[i]; var xdiff = tile.currentX-x; var ydiff = tile.currentY-y; var dist = Math.sqrt(xdiff*xdiff + ydiff*ydiff); var randRange = 220+(Math.random()*30); var range = randRange-dist; var force = 3*(range/randRange); if(force > tile.force){  tile.force = force;  var radians = Math.atan2(ydiff, xdiff);  tile.moveX = Math.cos(radians);  tile.moveY = Math.sin(radians);  tile.moveRotation = 0.5-Math.random(); } } tiles.sort(zindexSort); processFrame();}function zindexSort(a, b){ return (a.force-b.force);}function dropBomb(evt, obj){ var posx = 0; var posy = 0; var e = evt || window.event; if (e.pageX || e.pageY){ posx = e.pageX; posy = e.pageY; }else if (e.clientX || e.clientY) { posx = e.clientX + document.body.scrollLeft + document.documentElement.scrollLeft; posy = e.clientY + document.body.scrollTop + document.documentElement.scrollTop; } var canvasX = posx-obj.offsetLeft; var canvasY = posy-obj.offsetTop; explode(canvasX, canvasY);}function Tile(){ this.originX = 0; this.originY = 0; this.currentX = 0; this.currentY = 0; this.rotation = 0; this.force = 0; this.z = 0; this.moveX= 0; this.moveY= 0; this.moveRotation = 0; this.videoX = 0; this.videoY = 0;}/* getPixel return pixel object {r,g,b,a}*/function getPixel(imageData, x, y){ var data = imageData.data; var pos = (x + y * imageData.width) * 4; return {r:data[pos], g:data[pos+1], b:data[pos+2], a:data[pos+3]}}/* setPixel set pixel object {r,g,b,a}*/function setPixel(imageData, x, y, pixel){ var data = imageData.data; var pos = (x + y * imageData.width) * 4; data[pos] = pixel.r; data[pos+1] = pixel.g; data[pos+2] = pixel.b; data[pos+3] = pixel.a;}/* copyPixel faster then using getPixel/setPixel combo*/function copyPixel(sImageData, sx, sy, dImageData, dx, dy){ var spos = (sx + sy * sImageData.width) * 4; var dpos = (dx + dy * dImageData.width) * 4; dImageData.data[dpos] = sImageData.data[spos];   //R dImageData.data[dpos+1] = sImageData.data[spos+1]; //G dImageData.data[dpos+2] = sImageData.data[spos+2]; //B dImageData.data[dpos+3] = sImageData.data[spos+3]; //A}</script>