<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8"/>
<meta name="viewport" content="width=device-width"/>
<title>烟花</title>
<style type="text/css">
body{
background-color: black;
margin: 0;
}
#canvas{
cursor: pointer;
}
</style>
</head>
<body>
<canvas id="canvas"></canvas>
<script type="text/javascript">
window.requestAnimFrame = (function () {
return window.requestAnimFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function(callback){
window.setTimeout(callback,1000 / 60);
};
})();
Function.prototype.extend = function (oContext, bIsStatic) {
var oThis = (typeof bIsStatic != 'undefined' && bIsStatic)? this: this.prototype;
for ( var prop in oContext) {
oThis[prop] = oContext[prop];
}
}
var opt = {
canvas : document.getElementById('canvas'),
ctx: document.getElementById('canvas').getContext('2d'),
w: window.innerWidth,
h: window.innerHeight,
fireworks: [],//烟花
grains: [],//粒子
x: 0,
y: 0,
mousedown: false,
hue: 0,//色调
totalLimite: 5,
limite: 0,
totalTime: 80,
time: 0
};
opt.canvas.width = opt.w;
opt.canvas.height = opt.h;
function random(min,max){
return Math.random()*(max-min)+min;
}
function calcuDis(x1,y1,x2,y2){
return Math.sqrt(Math.pow(x1-x2,2)+Math.sqrt(y1-y2,2));
}
function Firework( x1, y1, x2, y2 ) {
this.x = this.x1 = x1;
this.y = this.y1 = y1;
this.x2 = x2;
this.y2 = y2;
this.target = calcuDis( x1, y1, x2, y2 );
this.distance = 0;
this.position = [];
for(var i = 2; i >= 0; i--) {
this.position.push( [ this.x, this.y ] );
}
this.angle = Math.atan2( y2 - y1, x2 - x1 );
this.speed = 2;
this.acceleration = 1.05;//加速度
this.lightness = random( 50, 70 );
this.targetRadius = 1;
}
Firework.extend({
update: function(index) {
this.position.pop();
this.position.unshift( [ this.x, this.y ] );
if( this.targetRadius < 8 ) {
this.targetRadius += 0.3;
} else {
this.targetRadius = 1;
}
this.speed *= this.acceleration;
var x = Math.cos( this.angle ) * this.speed,
y = Math.sin( this.angle ) * this.speed;
this.distance = calcuDis( this.x1, this.y1, this.x + x, this.y + y );
if( this.distance >= this.target ) {
for(var i = 50; i >= 0; i--) {
opt.grains.push( new Grain( this.x2, this.y2 ) );
}
opt.fireworks.splice( index, 1 );
} else {
this.x += x;
this.y += y;
}
},
draw: function() {
opt.ctx.beginPath();
opt.ctx.moveTo( this.position[ this.position.length - 1][ 0 ], this.position[ this.position.length - 1][ 1 ] );
opt.ctx.lineTo( this.x, this.y );
opt.ctx.strokeStyle = 'hsl(' + opt.hue + ', 100%, ' + this.lightness + '%)';
opt.ctx.stroke();
opt.ctx.closePath();
opt.ctx.beginPath();
opt.ctx.arc( this.x2, this.y2, this.targetRadius, 0, Math.PI * 2 );
opt.ctx.stroke();
opt.ctx.closePath();
}
});
function Grain( x, y ) {
this.x = x;
this.y = y;
this.position = [];
for(var i = 4; i >= 0; i--) {
this.position.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( opt.hue - 10, opt.hue + 10 );
this.lightness = random( 50, 80 );
this.alpha = 1;
this.decay = random( 0.01, 0.03 );
}
Grain.extend({
update: function(index) {
this.position.pop();
this.position.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 ) {
opt.grains.splice( index, 1 );
}
},
draw: function() {
opt.ctx.beginPath();
opt.ctx.moveTo( this.position[ this.position.length - 1 ][ 0 ], this.position[ this.position.length - 1 ][ 1 ] );
opt.ctx.lineTo( this.x, this.y );
opt.ctx.strokeStyle = 'hsla(' + this.hue + ', 100%, ' + this.lightness + '%, ' + this.alpha + ')';
opt.ctx.stroke();
opt.ctx.closePath();
}
});
function loop(){
opt.ctx.globalCompositeOperation = 'destination-out';
opt.ctx.fillStyle = 'rgba(0, 0, 0, 0.5)';
opt.ctx.fillRect( 0, 0, opt.w, opt.h );
opt.ctx.globalCompositeOperation = 'lighter';
opt.hue += 0.5;
var i = opt.fireworks.length;
while( i-- ) {
opt.fireworks[ i ].draw();
opt.fireworks[ i ].update( i );
}
i = opt.grains.length;
while( i-- ) {
opt.grains[ i ].draw();
opt.grains[ i ].update( i );
}
if( opt.time >= opt.totalTime ) {
if( !opt.mousedown ) {
opt.fireworks.push( new Firework( opt.w / 2, opt.h, random( 0, opt.w ), random( 0, opt.h / 2 ) ) );
opt.time= 0;
}
} else {
opt.time++;
}
if( opt.limite >= opt.totalLimite ) {
if( opt.mousedown ) {
opt.fireworks.push( new Firework( opt.w / 2, opt.h, opt.x, opt.y ) );
opt.limite = 0;
}
} else {
opt.limite++;
}
requestAnimFrame(loop);
}
opt.canvas.onmousemove = function(e){
opt.x = e.pageX - opt.canvas.offsetLeft;
opt.y = e.pageY - opt.canvas.offsetTop;
}
opt.canvas.onmousedown = function(e){
opt.mousedown = true;
}
opt.canvas.onmouseup = function(e){
opt.mousedown = false;
}
window.onload= function(){
loop();
};
</script>
</body>
</html>
原文地址：http://www.w3cfuns.com/blog-5444049-5404365.html