canvas 爱心

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title>HTML5</title>
<style>
*{padding:0;margin:0;}   
canvas {
    display: block;
    background: #000;
    cursor: crosshair;
    display: block;
}
</style>
</head>
<body>
<canvas id="c"></canvas>
<script>
window.requestAnimFrame =
    window.requestAnimationFrame ||
    window.webkitRequestAnimationFrame ||
    window.mozRequestAnimationFrame ||
    window.oRequestAnimationFrame ||
    window.msRequestAnimationFrame ||
    function (callback) {
        window.setTimeout(callback, 1000 / 60);
};
var windW  = document.documentElement.clientWidth || document.body.clientWidth,
    windH  = document.documentElement.clientHeight ||document.body.clientHeight;

    canvas = document.getElementById('c');
    context = canvas.getContext('2d');

    canvas.width = windW;
    canvas.height = windH;

    originX = windW/2;
    originY = windH;


    var firesBox = firesBoxTmp = [],
        line = 20;    
        
    var Fireworks = function(px,sx,line,fire,dely){

        this.fire = fire;
        this.dely = dely;
        this.endX = px.x;
        this.endY = px.y;

        this.startX = sx.x;
        this.startY = sx.y;

        this.p1 = {
            x:sx.x,
            y:sx.y
        };
        var totallong = Math.sqrt((this.endX-this.p1.x) * (this.endX-this.p1.x) +(this.endY-this.p1.y) * (this.endY-this.p1.y));

        this.p2 = {
            x:(line*(this.endX-this.p1.x))/totallong+this.p1.x,
            y:(line*(this.endY-this.p1.y))/totallong+this.p1.y
        }

        this.color = {
            r:Math.round(Math.random()*255),
            g:Math.round(Math.random()*255),
            b:Math.round(Math.random()*255),
            a:Math.random()
        }
    }

    Fireworks.prototype.draw = function(){
        context.beginPath();
        context.moveTo(this.p1.x, this.p1.y);
        context.lineTo(this.p2.x, this.p2.y);
      //  context.strokeStyle =  'hsla(' + this.color.r + ', '+this.color.g+'%, ' + this.color.b + '%, ' + this.color.a + ')';
        context.strokeStyle =  'rgba(' + this.color.r + ', '+this.color.g+', ' + this.color.b + ', ' + this.color.a + ')';
        context.stroke();
        context.closePath();
    }

    Fireworks.prototype.update = function(){
        if(
            (this.endX<this.startX&&this.p1.x<this.endX)||
            (this.endX>=this.startX&&this.p1.x>=this.endX)
        ){
            if(!this.fire) firesBoxTmp.push(this);
            return ;
        }
        var dely  = this.dely;
        this.p1.x += (this.endX-this.startX)*dely;
        this.p1.y += (this.endY-this.startY)*dely;
        this.p2.x += (this.endX-this.startX)*dely;
        this.p2.y += (this.endY-this.startY)*dely;

        this.color.r+=5;

        if(
            (this.endX<this.startX&&this.p1.x>=this.endX)||
            (this.endX>=this.startX&&this.p1.x<=this.endX)
        ){
           firesBoxTmp.push(this);
        }else{
            firesBoxTmp.push(this);
            if(!this.fire){ 
                firesBoxTmp.push(this);
                return ;
            }
            var startP = {},endP={};

            startP.x = this.endX;
            startP.y = this.endY;

            for (var i=1;i<10;i++) {
                if(i!=5){
                    r = Math.random()*10;
                    endP.x = startP.x + Math.sin(2 * Math.PI * i * 36 / 360) * r;
                    endP.y = startP.y - Math.cos(2 * Math.PI * i * 36 / 360) * r;
                    fire = new Fireworks(endP,startP,Math.random()*line*.5,false,.013);
                    firesBoxTmp.push(fire);
                }
                
            }  
        }
    }
    function update(){
        requestAnimFrame(update);
        context.clearRect(0, 0, canvas.width, canvas.height);  
        var i = firesBox.length;
        if (i <= 0) return;
        while (i--) {
            firesBox[i].draw();
            firesBox[i].update();
        }
        firesBox = firesBoxTmp;
        firesBoxTmp = [];
        
    }

    function heartShape(){
        if(heartindex>=4.8){
            clearTimeout(heart);
        }
        var endP ={} ,startP = {},r=90,dx=windW/2,dy=windH/3;

        startP.x = originX;
        startP.y = originY;

        var m,n,x,y,i= heartindex;
        
        m = i;
        n = -r * (((Math.sin(i) * Math.sqrt(Math.abs(Math.cos(i)))) / (Math.sin(i) + 1.4)) - 2 * Math.sin(i) + 2);
        endP.x = n * Math.cos(m) + dx;
        endP.y = n * Math.sin(m) + dy;
        fire = new Fireworks(endP,startP,line,true,0.016);
        firesBox.push(fire);
        heartindex+=.04;
        
    }
    var heartindex = -1.56;
    var heart = setInterval(function(){
        heartShape();
    },10);
    window.onload = update;
    heartShape();
</script>
</body>
</html>

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