これは、私たちの生活に咲く花火のアニメーション特殊効果をシミュレートするものです。興味のある読者の皆さん、この効果を実装するプロセスとコードを簡単に分析してみましょう。参考にしてください
<!DOCTYPE HTML>
<html>
<head>
<title>Canvas 实现放烟花特效</title>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width,height=device-height,inital-scale=1.0,maximum-scale=1.0,user-scalable=no">
<style type="text/css">
html,body{height:100%;margin:0;padding:0}
ul,li{text-indent:0;text-decoration:none;margin:0;padding:0}
img{border:0}
body{background-color:#000;color:#999;font:100%/18px helvetica, arial, sans-serif}
canvas{cursor:crosshair;display:block;left:0;position:absolute;top:0;z-index:20}
#header img{width:100%; height:20%;}
#bg img{width:100%; height:80%;}
#header,#bg{position:fixed;left:0;right:0;z-index:10}
#header{top:0}
#bg{position:fixed;z-index:1;bottom:0}
audio{position:fixed;display:none;bottom:0;left:0;right:0;width:100%;z-index:5}
</style>
</head>
<body>
<p id="bg">
<img id="bgimg" src="http://img.ivsky.com/img/tupian/pre/201508/02/yuzhou_xingkong_yu_yueliang-006.jpg">
</p>
<script src="http://cdn.bootcss.com/jquery/2.2.0/jquery.min.js"></script>
<script>
$(function(){
var Fireworks = function(){
var self = this;
// 产生烟花随机数
var rand = function(rMi, rMa){
//按位取反运算符
return ~~((Math.random()*(rMa-rMi+1))+rMi);
},hitTest = function(x1, y1, w1, h1, x2, y2, w2, h2){
return !(x1 + w1 < x2 || x2 + w2 < x1 || y1 + h1 < y2 || y2 + h2 < y1);
};
//请求动画帧
window.requestAnimFrame=function(){
return window.requestAnimationFrame
||window.webkitRequestAnimationFrame
||window.mozRequestAnimationFrame
||window.oRequestAnimationFrame
||window.msRequestAnimationFrame
||function(callback){
window.setTimeout(callback,1000/60);
}
}();
self.init = function(){
self.canvas = document.createElement('canvas');
//canvas 全屏
selfself.canvas.width = self.cw = $(window).innerWidth();
selfself.canvas.height = self.ch = $(window).innerHeight();
self.particles = [];
self.partCount = 150;
self.fireworks = [];
selfself.mx = self.cw/2;
selfself.my = self.ch/2;
self.currentHue = 30;
self.partSpeed = 5;
self.partSpeedVariance = 10;
self.partWind = 50;
self.partFriction = 5;
self.partGravity = 1;
self.hueMin = 0;
self.hueMax = 360;
self.fworkSpeed = 4;
self.fworkAccel = 10;
self.hueVariance = 30;
self.flickerDensity = 25;
self.showShockwave = true;
self.showTarget = false;
self.clearAlpha = 25;
$(document.body).append(self.canvas);
selfself.ctx = self.canvas.getContext('2d');
self.ctx.lineCap = 'round';
self.ctx.lineJoin = 'round';
self.lineWidth = 1;
self.bindEvents();
self.canvasLoop();
self.canvas.onselectstart = function() {
return false;
};
};
// 创建粒子
self.createParticles = function(x,y, hue){
var countdown = self.partCount;
while(countdown--){
var newParticle = {
x: x,
y: y,
coordLast: [
{x: x, y: y},
{x: x, y: y},
{x: x, y: y}
],
angle: rand(0, 360),
speed: rand(((self.partSpeed - self.partSpeedVariance) <= 0) ? 1 : self.partSpeed - self.partSpeedVariance, (self.partSpeed + self.partSpeedVariance)),
friction: 1 - self.partFriction/100,
gravity: self.partGravity/2,
hue: rand(hue-self.hueVariance, hue+self.hueVariance),
brightness: rand(50, 80),
alpha: rand(40,100)/100,
decay: rand(10, 50)/1000,
wind: (rand(0, self.partWind) - (self.partWind/2))/25,
lineWidth: self.lineWidth
};
self.particles.push(newParticle);
}
};
// 更新粒子
self.updateParticles = function(){
var i = self.particles.length;
while(i--){
var p = self.particles[i];
var radians = p.angle * Math.PI / 180;
var vx = Math.cos(radians) * p.speed;
var vy = Math.sin(radians) * p.speed;
p.speed *= p.friction;
p.coordLast[2].x = p.coordLast[1].x;
p.coordLast[2].y = p.coordLast[1].y;
p.coordLast[1].x = p.coordLast[0].x;
p.coordLast[1].y = p.coordLast[0].y;
p.coordLast[0].x = p.x;
p.coordLast[0].y = p.y;
p.x += vx;
p.y += vy;
p.y += p.gravity;
p.angle += p.wind;
p.alpha -= p.decay;
if(!hitTest(0,0,self.cw,self.ch,p.x-p.radius, p.y-p.radius, p.radius*2, p.radius*2) || p.alpha < .05){
self.particles.splice(i, 1);
}
};
};
// 绘制粒子
self.drawParticles = function(){
var i = self.particles.length;
while(i--){
var p = self.particles[i];
var coordRand = (rand(1,3)-1);
self.ctx.beginPath();
self.ctx.moveTo(Math.round(p.coordLast[coordRand].x), Math.round(p.coordLast[coordRand].y));
self.ctx.lineTo(Math.round(p.x), Math.round(p.y));
self.ctx.closePath();
self.ctx.strokeStyle = 'hsla('+p.hue+', 100%, '+p.brightness+'%, '+p.alpha+')';
self.ctx.stroke();
if(self.flickerDensity > 0){
var inverseDensity = 50 - self.flickerDensity;
if(rand(0, inverseDensity) === inverseDensity){
self.ctx.beginPath();
self.ctx.arc(Math.round(p.x), Math.round(p.y), rand(p.lineWidth,p.lineWidth+3)/2, 0, Math.PI*2, false)
self.ctx.closePath();
var randrandAlpha = rand(50,100)/100;
self.ctx.fillStyle = 'hsla('+p.hue+', 100%, '+p.brightness+'%, '+randAlpha+')';
self.ctx.fill();
}
}
};
};
// 创建烟花
self.createFireworks = function(startX, startY, targetX, targetY){
var newFirework = {
x: startX,
y: startY,
startX: startX,
startY: startY,
hitX: false,
hitY: false,
coordLast: [
{x: startX, y: startY},
{x: startX, y: startY},
{x: startX, y: startY}
],
targetX: targetX,
targetY: targetY,
speed: self.fworkSpeed,
angle: Math.atan2(targetY - startY, targetX - startX),
shockwaveAngle: Math.atan2(targetY - startY, targetX - startX)+(90*(Math.PI/180)),
acceleration: self.fworkAccel/100,
hue: self.currentHue,
brightness: rand(50, 80),
alpha: rand(50,100)/100,
lineWidth: self.lineWidth
};
self.fireworks.push(newFirework);
};
// 更新烟花
self.updateFireworks = function(){
var i = self.fireworks.length;
while(i--){
var f = self.fireworks[i];
self.ctx.lineWidth = f.lineWidth;
vx = Math.cos(f.angle) * f.speed,
vy = Math.sin(f.angle) * f.speed;
f.speed *= 1 + f.acceleration;
f.coordLast[2].x = f.coordLast[1].x;
f.coordLast[2].y = f.coordLast[1].y;
f.coordLast[1].x = f.coordLast[0].x;
f.coordLast[1].y = f.coordLast[0].y;
f.coordLast[0].x = f.x;
f.coordLast[0].y = f.y;
if(f.startX >= f.targetX){
if(f.x + vx <= f.targetX){
ff.x = f.targetX;
f.hitX = true;
} else {
f.x += vx;
}
} else {
if(f.x + vx >= f.targetX){
ff.x = f.targetX;
f.hitX = true;
} else {
f.x += vx;
}
}
if(f.startY >= f.targetY){
if(f.y + vy <= f.targetY){
ff.y = f.targetY;
f.hitY = true;
} else {
f.y += vy;
}
} else {
if(f.y + vy >= f.targetY){
ff.y = f.targetY;
f.hitY = true;
} else {
f.y += vy;
}
}
if(f.hitX && f.hitY){
self.createParticles(f.targetX, f.targetY, f.hue);
self.fireworks.splice(i, 1);
}
};
};
// 绘制烟花
self.drawFireworks = function(){
var i = self.fireworks.length;
self.ctx.globalCompositeOperation = 'lighter';
while(i--){
var f = self.fireworks[i];
self.ctx.lineWidth = f.lineWidth;
var coordRand = (rand(1,3)-1);
self.ctx.beginPath();
self.ctx.moveTo(Math.round(f.coordLast[coordRand].x), Math.round(f.coordLast[coordRand].y));
self.ctx.lineTo(Math.round(f.x), Math.round(f.y));
self.ctx.closePath();
self.ctx.strokeStyle = 'hsla('+f.hue+', 100%, '+f.brightness+'%, '+f.alpha+')';
self.ctx.stroke();
if(self.showTarget){
self.ctx.save();
self.ctx.beginPath();
self.ctx.arc(Math.round(f.targetX), Math.round(f.targetY), rand(1,8), 0, Math.PI*2, false)
self.ctx.closePath();
self.ctx.lineWidth = 1;
self.ctx.stroke();
self.ctx.restore();
}
if(self.showShockwave){
self.ctx.save();
self.ctx.translate(Math.round(f.x), Math.round(f.y));
self.ctx.rotate(f.shockwaveAngle);
self.ctx.beginPath();
self.ctx.arc(0, 0, 1*(f.speed/5), 0, Math.PI, true);
self.ctx.strokeStyle = 'hsla('+f.hue+', 100%, '+f.brightness+'%, '+rand(25, 60)/100+')';
self.ctx.lineWidth = f.lineWidth;
self.ctx.stroke();
self.ctx.restore();
}
};
};
// 绑定事件
self.bindEvents = function(){
$(window).on('resize', function(){
clearTimeout(self.timeout);
self.timeout = setTimeout(function() {
selfself.canvas.width = self.cw = $(window).innerWidth();
selfself.canvas.height = self.ch = $(window).innerHeight();
self.ctx.lineCap = 'round';
self.ctx.lineJoin = 'round';
}, 100);
});
$(self.canvas).on('mousedown', function(e){
self.mx = e.pageX - self.canvas.offsetLeft;
self.my = e.pageY - self.canvas.offsetTop;
self.currentHue = rand(self.hueMin, self.hueMax);
self.createFireworks(self.cw/2, self.ch, self.mx, self.my);
$(self.canvas).on('mousemove.fireworks', function(e){
self.mx = e.pageX - self.canvas.offsetLeft;
self.my = e.pageY - self.canvas.offsetTop;
self.currentHue = rand(self.hueMin, self.hueMax);
self.createFireworks(self.cw/2, self.ch, self.mx, self.my);
});
});
$(self.canvas).on('mouseup', function(e){
$(self.canvas).off('mousemove.fireworks');
});
};
self.clear = function(){
self.particles = [];
self.fireworks = [];
self.ctx.clearRect(0, 0, self.cw, self.ch);
};
self.canvasLoop = function(){
requestAnimFrame(self.canvasLoop, self.canvas);
self.ctx.globalCompositeOperation = 'destination-out';
self.ctx.fillStyle = 'rgba(0,0,0,'+self.clearAlpha/100+')';
self.ctx.fillRect(0,0,self.cw,self.ch);
self.updateFireworks();
self.updateParticles();
self.drawFireworks();
self.drawParticles();
};
self.init();
}
var fworks = new Fireworks();
$('#info-toggle').on('click', function(e){
$('#info-inner').stop(false, true).slideToggle(100);
e.preventDefault();
});
});
</script>
<canvas width="1400" height="449"></canvas>
</body>
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