HTML5 Canvas 破碎重组的视频特效的示例代码

        <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>