要过年啦，用canvas做了个烟火效果

2023-11-26 11:29:40

　　要过年了，过年想到的就是放烟火啦。。。。于是就用canvas写了个放烟火的效果，鼠标点击也会产生烟火，不过不要产生太多烟火哦，一个烟火散出的粒子是30到200个之间，当页面上的粒子数量达到一定的时候，页面就会很卡咯，我也没特意去优化神马的。以后有空再说吧。

　　直接上DEMO吧：放烟火

　　原理很简单。。。就写一个烟火类以及碎屑类，实例化后让它飞起来，然后到达某个点后，把这个烟火对象的dead属性置为true，然后再实例化出一定数量的碎屑对象，并且给与碎屑对象随机一个要到达的目标点，然后让所有碎屑对象飞过去就行了。

　　【烟火】

var Boom = function(x,r,c,boomArea,shape){  //烟火对象
            this.booms = [];
            this.x = x;
            this.y = (canvas.height+r);
            this.r = r;
            this.c = c;
            this.shape = shape || false;
            this.boomArea = boomArea;
            this.theta = 0;
            this.dead = false;
            this.ba = parseInt(getRandom(80 , 200));
        }
        Boom.prototype = {
            _paint:function(){  
                ctx.save();
                ctx.beginPath();
                ctx.arc(this.x,this.y,this.r,0,2*Math.PI);
                ctx.fillStyle = this.c;
                ctx.fill();
                ctx.restore();
            },
            _move:function(){
                var dx = this.boomArea.x - this.x , dy = this.boomArea.y - this.y;
                this.x = this.x+dx*0.01;
                this.y = this.y+dy*0.01;

                if(Math.abs(dx)<=this.ba && Math.abs(dy)<=this.ba){
                    if(this.shape){
                        this._shapBoom();
                    }
                    else this._boom();
                    this.dead = true;
                }
                else {
                    this._paint();
                }
            },
            _drawLight:function(){
                ctx.save();
                ctx.fillStyle = "rgba(255,228,150,0.3)";
                ctx.beginPath();
                ctx.arc(this.x , this.y , this.r+3*Math.random()+1 , 0 , 2*Math.PI);
                ctx.fill();
                ctx.restore();
            },
            _boom:function(){    //普通爆炸
                var fragNum = getRandom(30 , 200);
                var style = getRandom(0,10)>=5? 1 : 2;
                var color;
                if(style===1){
                    color = {
                        a:parseInt(getRandom(128,255)),
                        b:parseInt(getRandom(128,255)),
                        c:parseInt(getRandom(128,255))
                    }
                }

                var fanwei = parseInt(getRandom(300, 400));
                for(var i=0;i<fragNum;i++){
                    if(style===2){
                        color = {
                            a:parseInt(getRandom(128,255)),
                            b:parseInt(getRandom(128,255)),
                            c:parseInt(getRandom(128,255))
                        }
                    }
                    var a = getRandom(-Math.PI, Math.PI);
                    var x = getRandom(0, fanwei) * Math.cos(a) + this.x;
                    var y = getRandom(0, fanwei) * Math.sin(a) + this.y; 
                    var radius = getRandom(0 , 2)
                    var frag = new Frag(this.x , this.y , radius , color , x , y );
                    this.booms.push(frag);
                }
            },
            _shapBoom:function(){    //有形状的爆炸
                var that = this;
                putValue(ocas , octx , this.shape , 5, function(dots){
                    var dx = canvas.width/2-that.x;
                    var dy = canvas.height/2-that.y;
                    for(var i=0;i<dots.length;i++){
                        color = {a:dots[i].a,b:dots[i].b,c:dots[i].c}
                        var x = dots[i].x;
                        var y = dots[i].y;
                        var radius = 1;
                        var frag = new Frag(that.x , that.y , radius , color , x-dx , y-dy);
                        that.booms.push(frag);
                    }
                })
            }
        }

　　【碎屑】

var Frag = function(centerX , centerY , radius , color ,tx , ty){   //烟火碎屑对象
            this.tx = tx;
            this.ty = ty;
            this.x = centerX;
            this.y = centerY;
            this.dead = false;
            this.centerX = centerX;
            this.centerY = centerY;
            this.radius = radius;
            this.color = color;
        }

        Frag.prototype = {
            paint:function(){
                ctx.save();
                ctx.beginPath();
                ctx.arc(this.x , this.y , this.radius , 0 , 2*Math.PI);
                ctx.fillStyle = "rgba("+this.color.a+","+this.color.b+","+this.color.c+",1)";
                ctx.fill()
                ctx.restore();
            },
            moveTo:function(index){
                this.ty = this.ty+0.3;
                var dx = this.tx - this.x , dy = this.ty - this.y;
                this.x = Math.abs(dx)<0.1 ? this.tx : (this.x+dx*0.1);
                this.y = Math.abs(dy)<0.1 ? this.ty : (this.y+dy*0.1);
                if(dx===0 && Math.abs(dy)<=80){
                    this.dead = true;
                }
                this.paint();
            }
        }

　　让碎屑产生虚影也很简单，就是每次刷新画布时，不是擦掉重绘，而是绘制透明度为0.1（如果想虚影更长，可以把这个值弄的更小）的背景颜色。然后虚影就可以做出来了。也就是：

            ctx.save();
            ctx.fillStyle = "rgba(0,5,24,0.1)";
            ctx.fillRect(0,0,canvas.width,canvas.height);
            ctx.restore();

　　让烟火形成自己想要的形状，比如字体，图片之类的，也很简单，就是可以通过离屏canvas以及canvas的getImageData这个方法就可以做出来。离屏canvas，顾名思义就是离开屏幕的，也就是不可见的canvas，直接在js里面用document.createElement("canvas")就可以生成一个canvas dom对象了，只要不把这个dom对象赋给body，这个canvas对象就相当于一个离屏对象了，我们就可以获取到这个离屏canvas的context对象，然后再用户看不到的地方做任何我们想做的事情了。

　　让烟火形成自己想要的形状就是先把文字或者图片画在离屏canvas上，然后用getImageData获取画布上的像素数组，然后遍历数组，获取有颜色的像素，也就是我们想要的内容，保存起来后，再放到主canvas对象中显示出来。

　　getImageData的像素处理我之前的博客上有讲过，如果不会用的，请戳：随便谈谈用canvas来实现文字图片粒子化

　　下面贴出所有代码：

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
    <meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
    <style>
        body{margin:0;padding:0;overflow: hidden;}
        .city{width:100%;position:fixed;bottom: 0px;z-index: 100;}
        .city img{width: 100%;}
    </style>
    <title>放烟花</title>
</head>
<body onselectstart = "return false">
    <canvas id=‘cas‘ style="background-color:rgba(0,5,24,1)">浏览器不支持canvas</canvas>
    <div class="city"><img src="city.png" alt="" /></div>
    <img src="moon.png" alt="" id="moon" style="visibility: hidden;"/>
    <div style="display:none">
        <div class="shape">新年快乐</div>
        <div class="shape">合家幸福</div>
    </div>
    <script>
        var canvas = document.getElementById("cas");
        var ocas = document.createElement("canvas");
        var octx = ocas.getContext("2d");
        var ctx = canvas.getContext("2d");
        ocas.width = canvas.width = window.innerWidth;
        ocas.height = canvas.height = window.innerHeight;
        var bigbooms = [];
    
        window.onload = function(){
            initAnimate()
        }

        function initAnimate(){
            drawBg();

            lastTime = new Date();
            animate();
        }

        var lastTime;
        function animate(){  //动画
            ctx.save();
            ctx.fillStyle = "rgba(0,5,24,0.1)";
            ctx.fillRect(0,0,canvas.width,canvas.height);
            ctx.restore();


            var newTime = new Date();
            if(newTime-lastTime>1000){
                var random = Math.random()*100>2?true:false;
                var x = getRandom(canvas.width/4 , canvas.width*3/4);
                var y = getRandom(50 , 200);
                if(random){
                    var bigboom = new Boom(getRandom(canvas.width/3,canvas.width*2/3) ,2,"#FFF" , {x:x , y:y});
                    bigbooms.push(bigboom)
                }
                else {
                    var bigboom = new Boom(getRandom(canvas.width/3,canvas.width*2/3) ,2,"#FFF" , {x:canvas.width/2 , y:200} , document.querySelectorAll(".shape")[parseInt(getRandom(0, document.querySelectorAll(".shape").length))]);
                    bigbooms.push(bigboom)
                }
                lastTime = newTime;
                console.log(bigbooms)
            }

            stars.foreach(function(){
                this.paint();
            })

            drawMoon();

            bigbooms.foreach(function(index){
                var that = this;
                if(!this.dead){
                    this._move();
                    this._drawLight();
                }
                else{
                    this.booms.foreach(function(index){
                        if(!this.dead) {
                            this.moveTo(index);
                        }
                        else if(index === that.booms.length-1){
                            bigbooms[bigbooms.indexOf(that)] = null;
                        }
                    })
                }
            });
            
            raf(animate);
        }

        function drawMoon(){  //画月亮
            var moon = document.getElementById("moon");
            var centerX = canvas.width-200 , centerY = 100 , width = 80;
            if(moon.complete){
                ctx.drawImage(moon , centerX , centerY , width , width )
            }
            else {
                moon.onload = function(){
                    ctx.drawImage(moon ,centerX , centerY , width , width)
                }
            }
            var index = 0;
            for(var i=0;i<10;i++){
                ctx.save();
                ctx.beginPath();
                ctx.arc(centerX+width/2 , centerY+width/2 , width/2+index , 0 , 2*Math.PI);
                ctx.fillStyle="rgba(240,219,120,0.005)";
                index+=2;
                ctx.fill();
                ctx.restore();
            }
            
        }

        Array.prototype.foreach = function(callback){
            for(var i=0;i<this.length;i++){
                if(this[i]!==null) callback.apply(this[i] , [i])
            }
        }

        var raf = window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function (callback) { window.setTimeout(callback, 1000 / 60); };
         
        canvas.onclick = function(){
            var x = event.clientX;
            var y = event.clientY;
            var bigboom = new Boom(getRandom(canvas.width/3,canvas.width*2/3) ,2,"#FFF" , {x:x , y:y});
            bigbooms.push(bigboom)
        }

        //用于移动设备
        // canvas.addEventLisener("touchstart" , function(event){
        //     var touch = event.targetTouches[0];
        //     var x = event.pageX;
        //     var y = event.pageY;
        //     var bigboom = new Boom(getRandom(canvas.width/3,canvas.width*2/3) ,2,"#FFF" , {x:x , y:y});
        //     bigbooms.push(bigboom)
        // })

        var Boom = function(x,r,c,boomArea,shape){  //烟火对象
            this.booms = [];
            this.x = x;
            this.y = (canvas.height+r);
            this.r = r;
            this.c = c;
            this.shape = shape || false;
            this.boomArea = boomArea;
            this.theta = 0;
            this.dead = false;
            this.ba = parseInt(getRandom(80 , 200));
        }
        Boom.prototype = {
            _paint:function(){  
                ctx.save();
                ctx.beginPath();
                ctx.arc(this.x,this.y,this.r,0,2*Math.PI);
                ctx.fillStyle = this.c;
                ctx.fill();
                ctx.restore();
            },
            _move:function(){
                var dx = this.boomArea.x - this.x , dy = this.boomArea.y - this.y;
                this.x = this.x+dx*0.01;
                this.y = this.y+dy*0.01;

                if(Math.abs(dx)<=this.ba && Math.abs(dy)<=this.ba){
                    if(this.shape){
                        this._shapBoom();
                    }
                    else this._boom();
                    this.dead = true;
                }
                else {
                    this._paint();
                }
            },
            _drawLight:function(){
                ctx.save();
                ctx.fillStyle = "rgba(255,228,150,0.3)";
                ctx.beginPath();
                ctx.arc(this.x , this.y , this.r+3*Math.random()+1 , 0 , 2*Math.PI);
                ctx.fill();
                ctx.restore();
            },
            _boom:function(){    //普通爆炸
                var fragNum = getRandom(30 , 200);
                var style = getRandom(0,10)>=5? 1 : 2;
                var color;
                if(style===1){
                    color = {
                        a:parseInt(getRandom(128,255)),
                        b:parseInt(getRandom(128,255)),
                        c:parseInt(getRandom(128,255))
                    }
                }

                var fanwei = parseInt(getRandom(300, 400));
                for(var i=0;i<fragNum;i++){
                    if(style===2){
                        color = {
                            a:parseInt(getRandom(128,255)),
                            b:parseInt(getRandom(128,255)),
                            c:parseInt(getRandom(128,255))
                        }
                    }
                    var a = getRandom(-Math.PI, Math.PI);
                    var x = getRandom(0, fanwei) * Math.cos(a) + this.x;
                    var y = getRandom(0, fanwei) * Math.sin(a) + this.y; 
                    var radius = getRandom(0 , 2)
                    var frag = new Frag(this.x , this.y , radius , color , x , y );
                    this.booms.push(frag);
                }
            },
            _shapBoom:function(){    //有形状的爆炸
                var that = this;
                putValue(ocas , octx , this.shape , 5, function(dots){
                    var dx = canvas.width/2-that.x;
                    var dy = canvas.height/2-that.y;
                    for(var i=0;i<dots.length;i++){
                        color = {a:dots[i].a,b:dots[i].b,c:dots[i].c}
                        var x = dots[i].x;
                        var y = dots[i].y;
                        var radius = 1;
                        var frag = new Frag(that.x , that.y , radius , color , x-dx , y-dy);
                        that.booms.push(frag);
                    }
                })
            }
        }

        function putValue(canvas , context , ele , dr , callback){  //在离屏canvas中画上自己想要的形状，然后获取像素数组
            context.clearRect(0,0,canvas.width,canvas.height);
            var img = new Image();
            if(ele.innerHTML.indexOf("img")>=0){
                img.src = ele.getElementsByTagName("img")[0].src;
                imgload(img , function(){
                    context.drawImage(img , canvas.width/2 - img.width/2 , canvas.height/2 - img.width/2);
                    dots = getimgData(canvas , context , dr);
                    callback(dots);
                })
            }
            else {
                var text = ele.innerHTML;
                context.save();
                var fontSize =200;
                context.font = fontSize+"px 宋体 bold";
                context.textAlign = "center";
                context.textBaseline = "middle";
                context.fillStyle = "rgba("+parseInt(getRandom(128,255))+","+parseInt(getRandom(128,255))+","+parseInt(getRandom(128,255))+" , 1)";
                context.fillText(text , canvas.width/2 , canvas.height/2);
                context.restore();
                dots = getimgData(canvas , context , dr);
                callback(dots);
            }
        }

        function imgload(img , callback){
            if(img.complete){
                callback.call(img);
            }
            else {
                img.onload = function(){
                    callback.call(this);
                }
            }
        }

        function getimgData(canvas , context , dr){   //获取像素数组
            var imgData = context.getImageData(0,0,canvas.width , canvas.height);
            context.clearRect(0,0,canvas.width , canvas.height);
            var dots = [];
            for(var x=0;x<imgData.width;x+=dr){
                for(var y=0;y<imgData.height;y+=dr){
                    var i = (y*imgData.width + x)*4;
                    if(imgData.data[i+3] > 128){
                        var dot = {x:x , y:y , a:imgData.data[i] , b:imgData.data[i+1] , c:imgData.data[i+2]};
                        dots.push(dot);
                    }
                }
            }
            return dots;
        }

        function getRandom(a , b){
            return Math.random()*(b-a)+a;
        }


        var maxRadius = 1 , stars=[];
        function drawBg(){
            for(var i=0;i<100;i++){
                var r = Math.random()*maxRadius;
                var x = Math.random()*canvas.width;
                var y = Math.random()*2*canvas.height - canvas.height;
                var star = new Star(x , y , r);
                stars.push(star);
                star.paint()
            }

        }

        var Star = function(x,y,r){
            this.x = x;this.y=y;this.r=r;
        }
        Star.prototype = {
            paint:function(){
                ctx.save();
                ctx.beginPath();
                ctx.arc(this.x , this.y , this.r , 0 , 2*Math.PI);
                ctx.fillStyle = "rgba(255,255,255,"+this.r+")";
                ctx.fill();
                ctx.restore();
            }
        }

        var focallength = 250;
        var Frag = function(centerX , centerY , radius , color ,tx , ty){   //烟火碎屑对象
            this.tx = tx;
            this.ty = ty;
            this.x = centerX;
            this.y = centerY;
            this.dead = false;
            this.centerX = centerX;
            this.centerY = centerY;
            this.radius = radius;
            this.color = color;
        }

        Frag.prototype = {
            paint:function(){
                ctx.save();
                ctx.beginPath();
                ctx.arc(this.x , this.y , this.radius , 0 , 2*Math.PI);
                ctx.fillStyle = "rgba("+this.color.a+","+this.color.b+","+this.color.c+",1)";
                ctx.fill()
                ctx.restore();
            },
            moveTo:function(index){
                this.ty = this.ty+0.3;
                var dx = this.tx - this.x , dy = this.ty - this.y;
                this.x = Math.abs(dx)<0.1 ? this.tx : (this.x+dx*0.1);
                this.y = Math.abs(dy)<0.1 ? this.ty : (this.y+dy*0.1);
                if(dx===0 && Math.abs(dy)<=80){
                    this.dead = true;
                }
                this.paint();
            }
        }
    </script>
</body>
</html>

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要过年啦，用canvas做了个烟火效果

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