canvas绘图粒子扩散效果【原创】

第一次写canvas相关的脚本，点击页面可以产生新的扩散点，并整体颜色变换，可以根据输入数字变换粒子大小，

预览地址：http://runjs.cn/code/58mct5yo

<!-- lang: js -->
/*

@author-fanqie [email protected]
/
window.requestAnimFrame = (function(){
return window.requestAnimationFrame ||

      window.webkitRequestAnimationFrame ||
      window.mozRequestAnimationFrame    ||
      function( callback ){
        window.setTimeout(callback, 1000 / 60);
      };

})();
var openBtn=document.getElementById('J_open_btn');
var clearBtn=document.getElementById('J_clear_btn');
var runState=true;
//打开关闭
openBtn.addEventListener(“click”,function(e){

thisBtn=e.target;
if(runState==false){
    runState=true;
    thisBtn.innerHTML="停止";
}else{
    runState=false;
    thisBtn.innerHTML="继续";
}

});
//J_clear_btn
clearBtn.addEventListener(“click”,function(e){
liziDrawObj.destory();
runState=true;
thisBtn.innerHTML=“停止”;
});
var mycanvas=document.getElementById('I_mycanvas');
mycanvas.height=window.innerHeight;
mycanvas.width=window.innerWidth;
var colors=['#00FF00','#FFFF00','#FF0000','#00CCFF'];
var liziDrawClass=function(canvasObj,direction,directionVal,size,color){

this.canvasObj=canvasObj.getContext("2d");
this.direction=direction;//left top bottom right
this.directionVal=directionVal;//偏移量
this.size=size;
this.color=color;
this.liziItem=Array();//粒子对象集合

}
liziDrawClass.prototype={

//初始化
init:function(){
    liziDrawObj.factory(250,200);
    this.canvasObj.shadowColor=this.color;
    this.canvasObj.fillStyle=this.color;
    this.canvasObj.globalAlpha=this.size;
    this.canvasObj.shadowBlur=5;
    this.canvasObj.save();
},
//渲染画布
drawDraw:function(lizi){
    this.canvasObj.beginPath();


    this.canvasObj.arc(lizi.positionX,lizi.positionY,this.size,0,2*Math.PI);
    this.canvasObj.fill();
    this.canvasObj.closePath();
    this.canvasObj.restore();
},
//更新画布
update:function(){
        for(index in liziDrawObj.liziItem){

            liziDrawObj.liziItem[index]=liziDrawObj.createNew(liziDrawObj.liziItem[index],5);
            var liziList= liziDrawObj.liziItem[index];
            for(current in liziList){
                lizi=liziList[current];

                //liziDrawObj.canvasObj.clearRect(0,0,window.innerWidth,window.innerHeight);
                liziDrawObj.drawDraw(lizi);
            }
        }
},//同时创建多个新粒子 为了加快粒子产生速度 
createNew:function(liziList,count){
    lastLizi=liziList.pop();
    liziList=Array();
    liziList.push(lastLizi);
    for (var i = 0; i <count; i++) {
        lastLizi=liziList[liziList.length-1];

        var liziNew=new liziClass(lastLizi.size,
            lastLizi.color,
            lastLizi.direction,
            lastLizi.positionX,
            lastLizi.positionY,
            lastLizi.directionVal);
            liziNew.centerX=lastLizi.centerX;
            liziNew.centerY=lastLizi.centerY;
            liziNew.angle=lastLizi.angle+0.15;
            liziNew.directionVal=lastLizi.directionVal+0.05;
            cx= liziNew.centerX+Math.sin(liziNew.angle) * liziNew.directionVal;
            cy= liziNew.centerY+Math.cos(liziNew.angle) * liziNew.directionVal;
            liziNew.positionX=cx+Math.random();
            liziNew.positionY=cy+Math.random()*5;
            liziList.push(liziNew);
    };

    return liziList;
},
//生产粒子model
factory:function(positionX,positionY){
    var lizi=new liziClass(this.size, this.color,this.direction,positionX,positionY,this.directionVal);
    this.liziItem.push([lizi]);
   this.color=colors[parseInt(Math.random()*4,10)];
    this.canvasObj.shadowColor=this.color;
    this.canvasObj.fillStyle=this.color;
    this.canvasObj.save();
},destory:function(){
    this.canvasObj.clearRect(0,0,window.innerWidth,window.innerHeight);
    this.liziItem=new Array();
}

}
var liziClass=function(size,color,movement,positionX,positionY,directionVal){

    this.size=size;
    this.color=color;
    this.movement=movement;
    this.positionX=positionX;
    this.positionY=positionY;
    this.centerX=Number(positionX)-directionVal;
    this.centerY=Number(positionY)-directionVal;
    this.angle=0;
    this.directionVal=directionVal;//偏移量
}

liziClass.prototype={}

liziDrawObj.init();

function loop(){
    if(runState){
        liziDrawObj.size=document.getElementById('J_size').value;
        liziDrawObj.update();
    }
    requestAnimFrame(loop);

}
mycanvas.addEventListener("click",newPosition);
function newPosition(e){
    if(runState){
        liziDrawObj.factory(e.x,e.y);
    }
}
loop();
<!-- lang: html -->
   <a href="javascript:;" id="J_open_btn">停止</a>

清空

 <canvas id="I_mycanvas" class="mycanvas" >
     不支持……
 </canvas>

<!-- lang: css -->
.mycanvas{background: #000}
body{background: #eee}

.sizeInput{width: 2em;font-size:15px; }