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】
XML/HTML Code复制内容到剪贴板
- 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;
- thisthis.x = this.x+dx*0.01;
- thisthis.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】
XML/HTML Code复制内容到剪贴板
- 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){
- thisthis.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：
XML/HTML Code复制内容到剪贴板
- ctx.save();
- ctx.fillStyle = "rgba(0,5,24,0.1)";
- ctx.fillRect(0,0,canvas.width,canvas.height);
- ctx.restore();