标签：
<!DOCTYPE html>
<html>
<head>
<style>
body{background:#000;margin:0;}
canvas{cursor:crosshair;display:block;}
</style>
</head>
<body>
<canvas id="canvas">Canvas is not supported in your browser.</canvas>
<script>
window.requestAnimFrame=(function(){
return window.requestAnimationFrame||window.webkitRequestAnimationFrame||window.mozRequestAnimationFrame||function(callback){
window.setTimeout(callback,1000/60)
}
})();
var canvas=document.getElementById("canvas"),ctx=canvas.getContext("2d"),cw=window.innerWidth,ch=window.innerHeight,fireworks=[],particles=[],hue=120,limiterTotal=5,limiterTick=0,timerTotal=80,timerTick=0,mousedown=false,mx,my;canvas.width=cw;canvas.height=ch;
function random(min,max){return Math.random()*(max-min)+min}
function calculateDistance(p1x,p1y,p2x,p2y){
var xDistance=p1x-p2x,yDistance=p1y-p2y;
return Math.sqrt(Math.pow(xDistance,2)+Math.pow(yDistance,2))
}
function Firework(sx,sy,tx,ty){
this.x=sx;
this.y=sy;
this.sx=sx;
this.sy=sy;
this.tx=tx;
this.ty=ty;
this.distanceToTarget=calculateDistance(sx,sy,tx,ty);
this.distanceTraveled=0;
this.coordinates=[];
this.coordinateCount=3;
while(this.coordinateCount--)
{
this.coordinates.push([this.x,this.y])
}
this.angle=Math.atan2(ty-sy,tx-sx);
this.speed=2;
this.acceleration=1.05;
this.brightness=random(50,70);
this.targetRadius=1
}
Firework.prototype.update=function(index){
this.coordinates.pop();
this.coordinates.unshift([this.x,this.y]);
if(this.targetRadius<8){
this.targetRadius+=0.3
}
else{
this.targetRadius=1
}
this.speed*=this.acceleration;
var vx=Math.cos(this.angle)*this.speed,vy=Math.sin(this.angle)*this.speed;
this.distanceTraveled=calculateDistance(this.sx,this.sy,this.x+vx,this.y+vy);
if(this.distanceTraveled>=this.distanceToTarget){
createParticles(this.tx,this.ty);
fireworks.splice(index,1)
}else{
this.x+=vx;this.y+=vy
}
};
Firework.prototype.draw=function(){
ctx.beginPath();
ctx.moveTo(this.coordinates[this.coordinates.length-1][0],this.coordinates[this.coordinates.length-1][1]);
ctx.lineTo(this.x,this.y);
ctx.strokeStyle="hsl("+hue+", 100%, "+this.brightness+"%)";
ctx.stroke();
ctx.beginPath();
ctx.arc(this.tx,this.ty,this.targetRadius,0,Math.PI*2);
ctx.stroke()
};
function Particle(x,y){
this.x=x;this.y=y;
this.coordinates=[];
this.coordinateCount=5;
while(this.coordinateCount--){
this.coordinates.push([this.x,this.y])
}
this.angle=random(0,Math.PI*2);
this.speed=random(1,10);
this.friction=0.95;
this.gravity=1;
this.hue=random(hue-20,hue+20);
this.brightness=random(50,80);
this.alpha=1;
this.decay=random(0.015,0.03)
}
Particle.prototype.update=function(index){
this.coordinates.pop();
this.coordinates.unshift([this.x,this.y]);
this.speed*=this.friction;
this.x+=Math.cos(this.angle)*this.speed;this.y+=Math.sin(this.angle)*this.speed+this.gravity;this.alpha-=this.decay;
if(this.alpha<=this.decay){
particles.splice(index,1)
}
};
Particle.prototype.draw=function(){
ctx.beginPath();
ctx.moveTo(this.coordinates[this.coordinates.length-1][0],this.coordinates[this.coordinates.length-1][1]);
ctx.lineTo(this.x,this.y);
ctx.strokeStyle="hsla("+this.hue+", 100%, "+this.brightness+"%, "+this.alpha+")";
ctx.stroke()
};
function createParticles(x,y){
var particleCount=30;
while(particleCount--){
particles.push(new Particle(x,y))
}
}
function loop(){
requestAnimFrame(loop);
hue+=0.5;
ctx.globalCompositeOperation="destination-out";
ctx.fillStyle="rgba(0, 0, 0, 0.5)";
ctx.fillRect(0,0,cw,ch);
ctx.globalCompositeOperation="lighter";
var i=fireworks.length;
while(i--){
fireworks[i].draw();fireworks[i].update(i)
}
var i=particles.length;
while(i--){
particles[i].draw();particles[i].update(i)
}
if(timerTick>=timerTotal){
if(!mousedown){
fireworks.push(new Firework(cw/2,ch,random(0,cw),random(0,ch/2)));
timerTick=0
}
}
else{ timerTick++}
if(limiterTick>=limiterTotal){
if(mousedown){
fireworks.push(new Firework(cw/2,ch,mx,my));
limiterTick=0
}
}
else{ limiterTick++}
}
canvas.addEventListener("mousemove",function(e){
mx=e.pageX-canvas.offsetLeft;
my=e.pageY-canvas.offsetTop
});
canvas.addEventListener("mousedown",function(e){
e.preventDefault();mousedown=true
});
canvas.addEventListener("mouseup",function(e){
e.preventDefault();mousedown=false
});
window.onload=loop;
</script>
</body>
</html>
标签：
原文地址：http://www.cnblogs.com/jiechen/p/4976248.html
