这是一个很酷的 HTML5 canvas 动画，它将模拟的是我们现实 生活 中烟花绽放的动画特效，效果非常逼真，但是毕竟是 电 脑模拟，带女 朋友 看就算了，效果还是差了点，呵呵。这个HT ML 5 Canvas动画有 一点 比较出色，就是其性能，Ch rom e上基本没有卡的感觉，就算你放出很多烟花也一样。
下面我们来 简单 分析一下实现这款HTML5烟花特效的过程及代码，主要由HTML代码、CSS代码以及Javascript代码组成，当然javascript代码是最 重要 的。
HTML代码：
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< div &nbs p; id =]gui] > </ div > < div id =]canvas-cont ai ner] > < div id =] mount ains2& PR ime; > </ div > < div id =&rdquo ;m ountains1″ > </ div > < div id =]s Kylin e] > </ div > </ div >
HTML的结构非常简单，即构造了一个canvas容器，我们会 利用 JS在这个容器中生成一个Canvas对象。看最后的JS代码你就会 知道 了。
CSS代码：
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# canvas -container { background : #000 url (bg. jpg ); h ei ght : 400px ; left : 50%; m arg in : - 200px 0 0 - 300px ; pos IT ion : absolute ; top : 50%; width : 600px ; z -i ndex : 2; } canvas { cursor : crosshair ; dis play : block ; position : relative ; z-index : 3; } canvas:active { cursor : crosshair ; } #skylin e { background : url (skyline.png) re PE at -x 50% 0; bottom bottom : 0; height : 135px ; left : 0; position : absolute ; width : 100%; z-index : 1; } #mounta ins1 { background : url (mountains1.png) repeat -x 40% 0; bottom bottom : 0; height : 200px ; left : 0; position : absolute ; width : 100%; z-index : 1; } #mounta ins2 { background : url (mountains2.png) repeat -x 30% 0; bottom bottom : 0; height : 250px ; left : 0; position : absolute ; width : 100%; z-index : 1; } #gui { right right : 0; position : fixed ; top : 0; z-index : 3; }
CSS代码没什么特别，主要也就定义一下背景色和边框之类的。
接下来是最重要的Javascript代码。
Javascript代码：
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self.init = function (){ self.dt = 0; self.oldTime = Date.now(); self.canvas = document.createElement( 'canvas' ); self.canvasContainer = $( '#canvas-container' ); VAR canvasContainerDisabled = document.getElementById( 'canvas-container' ); self.canvas.onselectstart = function () { return false ; }; self.canvas.width = self.cw = 600; self.canvas.height = self.ch = 400; self.particles = []; self.partCount = 30; self.fireworks = []; self.mx = self.cw/2; self.my = self.ch/2; self. current Hue = 170; self.partSpeed = 5; self.partSpeedVariance = 10; self.partWind = 50; self.partFriction = 5; self.partGravity = 1; self.hueMin = 150; self.hueMax = 200; self.fworkSpeed = 2; self.fworkAccel = 4; self.hueVariance = 30; self.flickerDensity = 20; self.showShockwave = false ; self.showTarget = true ; self.clearAlpha = 25; self.canvasContainer.append(self.canvas); self.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 ; }; };
这段JS代码主要是往canvas容器中构造一个Canvas对象，并且对这个canvas对象的 外观 以及动画属性作了初始化。
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var Particle = function (x, y, hue){ this .x = x; this .y = y; this .coordLast = [ {x: x, y: y}, {x: x, y: y}, {x: x, y: y} ]; this .angle = rand(0, 360 ); this .speed = rand(((self.partSpeed - self.partSpeedVariance) <= 0) ? 1 : self.partSpeed - self.partSpeedVariance, (self.partSpeed + self.partSpeedVariance)); this .friction = 1 - self.partFriction/100; this .gravity = self.partGravity/2; this .hue = rand(hue -s elf.hueVariance, hue+self.hueVariance); this . br ightness = rand(50, 80); this .alpha = rand(40,100)/100; this .decay = rand(10, 50)/1000; this .wind = (rand(0, self.partWind) - (self.partWind/2))/25; this .lineWidth = self.lineWidth; }; Particle.prototype.update = function (index){ var radians = this .angle * Math.PI / 180; var vx = Math.cos(radians) * this .speed; var vy = Math.sin(radians) * this .speed + this .gravity; this .speed *= this .friction; this .coordLast[2].x = this .coordLast[1].x; this .coordLast[2].y = this .coordLast[1].y; this .coordLast[1].x = this .coordLast[0].x; this .coordLast[1].y = this .coordLast[0].y; this .coordLast[0].x = this .x; this .coordLast[0].y = this .y; this .x += vx * self.dt; this .y += vy * self.dt; this .angle += this .wind; this .alpha -= this .decay; if (!hit test (0,0,self.cw,self.ch, this .x- this .radius, this .y- this .radius, this .radius*2, this .radius*2) || this .alpha < .05){ self.particles. splice (index, 1); } }; Particle.prototype.draw = function (){ var coordRand = (rand(1,3)-1); self.ctx.be gin Path(); self.ctx.moveTo(Math.round( this .coordLast[coordRand].x), Math.round( this .coordLast[coordRand].y)); self.ctx.l inet o(Math.round( this .x), Math.round( this .y)); self.ctx.closePath(); self.ctx. stroke Style = 'hsla(' + this .hue+ ', 100%, ' + this .brightness+ '%, ' + this .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( this .x), Math.round( this .y), rand( this .lineWidth, this .lineWidth+3)/2, 0, Math.PI*2, false ) self.ctx.closePath(); var randAlpha = rand(50,100)/100; self.ctx.fillStyle = 'hsla(' + this .hue+ ', 100%, ' + this .brightness+ '%, ' +randAlpha+ ')' ; self.ctx.fill(); } } };
这段JS代码的功能是实现烟花爆炸后的小颗粒的 绘制 ，从draw方法中可以看出，创建几个随机点，烟花颗粒即可在这个范围的随机点中散落。
JavaScript Code 复制内容到剪贴板
var Firework = function (startX, startY, targetX, targetY){ this .x = startX; this .y = startY; this .startX = startX; this .startY = startY; this .hitX = false ; this .hitY = false ; this .coordLast = [ {x: startX, y: startY}, {x: startX, y: startY}, {x: startX, y: startY} ]; this .targetX = targetX; this .targetY = targetY; this .speed = self.fworkSpeed; this .angle = Math.atan2(targetY - startY, targetX - startX); this .shockwaveAngle = Math.atan2(targetY - startY, targetX - startX)+(90*(Math.PI/180)); this .acceleration = self.fworkAccel/100; this .hue = self.currentHue; this .brightness = rand(50, 80); this .alpha = rand(50,100)/100; this .lineWidth = self.lineWidth; this .targetRadius = 1; }; Firework.prototype.update = function (index){ self.ctx.lineWidth = this .lineWidth; vx = Math.cos( this .angle) * this .speed, vy = Math.sin( this .angle) * this .speed; this .speed *= 1 + this .acceleration; this .coordLast[2].x = this .coordLast[1].x; this .coordLast[2].y = this .coordLast[1].y; this .coordLast[1].x = this .coordLast[0].x; this .coordLast[1].y = this .coordLast[0].y; this .coordLast[0].x = this .x; this .coordLast[0].y = this .y; if (self.showTarget){ if ( this .targetRadius < 8){ this .targetRadius += .25 * self.dt; } else { this .targetRadius = 1 * self.dt; } } if ( this .startX >= this .targetX){ if ( this .x + vx <= this .targetX){ this .x = this .targetX; this .hitX = true ; } else { this .x += vx * self.dt; } } else { if ( this .x + vx >= this .targetX){ this .x = this .targetX; this .hitX = true ; } else { this .x += vx * self.dt; } } if ( this .startY >= this .targetY){ if ( this .y + vy <= this .targetY){ this .y = this .targetY; this .hitY = true ; } else { this .y += vy * self.dt; } } else { if ( this .y + vy >= this .targetY){ this .y = this .targetY; this .hitY = true ; } else { this .y += vy * self.dt; } } if ( this .hitX && this .hitY){ var randE xp losion = rand(0, 9); self.createParticles( this .targetX, this .targetY, this .hue); self.fireworks.splice(index, 1); } }; Firework.prototype.draw = function (){ self.ctx.lineWidth = this .lineWidth; var coordRand = (rand(1,3)-1); self.ctx.beginPath(); self.ctx.moveTo(Math.round( this .coordLast[coordRand].x), Math.round( this .coordLast[coordRand].y)); self.ctx.lineTo(Math.round( this .x), Math.round( this .y)); self.ctx.closePath(); self.ctx.strokeStyle = 'hsla(' + this .hue+ ', 100%, ' + this .brightness+ '%, ' + this .alpha+ ')' ; self.ctx.stroke(); if (self.showTarget){ self.ctx.save(); self.ctx.beginPath(); self.ctx.arc(Math.round( this .targetX), Math.round( this .targetY), this .targetRadius, 0, Math.PI*2, false ) self.ctx.closePath(); self.ctx.lineWidth = 1; self.ctx.stroke(); self.ctx.re Store (); } if (self.showShockwave){ self.ctx.save(); self.ctx.translate(Math.round( this .x), Math.round( this .y)); self.ctx.rotate( this .shockwaveAngle); self.ctx.beginPath(); self.ctx.arc(0, 0, 1*( this .speed/5), 0, Math.PI, true ); self.ctx.strokeStyle = 'hsla(' + this .hue+ ', 100%, ' + this .brightness+ '%, ' +rand(25, 60)/100+ ')' ; self.ctx.lineWidth = this .lineWidth; self.ctx.stroke(); self.ctx.restore(); } };
这段JS代码是创建烟花实例的，我们也可以从draw方法中看出，当我们鼠标点击 画布 中的某点时，烟花发射的目的地就在那个点上。
这款HTML5 Canvas烟花效果的核心代码就是这样，谢谢阅读，希望能帮到大家，请继续关注，我们会 努力 分享更多优秀的 文章 。
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