js烟花特效

2023-07-24 10:16:40

<!DOCTYPE html>
<html>
<head>
<style>
body{background:#000;margin:0;}
canvas{cursor:crosshair;display:block;}
</style>
</head>
<body>
<canvas id="canvas">Canvas is not supported in your browser.</canvas>
<script>
   window.requestAnimFrame=(function(){
       return window.requestAnimationFrame||window.webkitRequestAnimationFrame||window.mozRequestAnimationFrame||function(callback){
               window.setTimeout(callback,1000/60)
           }
   })();

   var canvas=document.getElementById("canvas"),ctx=canvas.getContext("2d"),cw=window.innerWidth,ch=window.innerHeight,fireworks=[],particles=[],hue=120,limiterTotal=5,limiterTick=0,timerTotal=80,timerTick=0,mousedown=false,mx,my;canvas.width=cw;canvas.height=ch;

   function random(min,max){return Math.random()*(max-min)+min}

   function calculateDistance(p1x,p1y,p2x,p2y){
       var xDistance=p1x-p2x,yDistance=p1y-p2y;
       return Math.sqrt(Math.pow(xDistance,2)+Math.pow(yDistance,2))
   }

   function Firework(sx,sy,tx,ty){
       this.x=sx;
       this.y=sy;
       this.sx=sx;
       this.sy=sy;
       this.tx=tx;
       this.ty=ty;
       this.distanceToTarget=calculateDistance(sx,sy,tx,ty);
       this.distanceTraveled=0;
       this.coordinates=[];
       this.coordinateCount=3;
       while(this.coordinateCount--)
           {
               this.coordinates.push([this.x,this.y])
           }
       this.angle=Math.atan2(ty-sy,tx-sx);
       this.speed=2;
       this.acceleration=1.05;
       this.brightness=random(50,70);
       this.targetRadius=1
   }

   Firework.prototype.update=function(index){
       this.coordinates.pop();
       this.coordinates.unshift([this.x,this.y]);
       if(this.targetRadius<8){
           this.targetRadius+=0.3
       }
           else{
               this.targetRadius=1
           }
           this.speed*=this.acceleration;
           var vx=Math.cos(this.angle)*this.speed,vy=Math.sin(this.angle)*this.speed;
           this.distanceTraveled=calculateDistance(this.sx,this.sy,this.x+vx,this.y+vy);
           if(this.distanceTraveled>=this.distanceToTarget){
               createParticles(this.tx,this.ty);
               fireworks.splice(index,1)
           }else{
               this.x+=vx;this.y+=vy
           }
   };

   Firework.prototype.draw=function(){
       ctx.beginPath();
       ctx.moveTo(this.coordinates[this.coordinates.length-1][0],this.coordinates[this.coordinates.length-1][1]);
       ctx.lineTo(this.x,this.y);
       ctx.strokeStyle="hsl("+hue+", 100%, "+this.brightness+"%)";
       ctx.stroke();
       ctx.beginPath();
       ctx.arc(this.tx,this.ty,this.targetRadius,0,Math.PI*2);
       ctx.stroke()
   };

   function Particle(x,y){
       this.x=x;this.y=y;
       this.coordinates=[];
       this.coordinateCount=5;
       while(this.coordinateCount--){
           this.coordinates.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(hue-20,hue+20);
       this.brightness=random(50,80);
       this.alpha=1;
       this.decay=random(0.015,0.03)
   }

   Particle.prototype.update=function(index){
       this.coordinates.pop();
       this.coordinates.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){
           particles.splice(index,1)
       }
   };

   Particle.prototype.draw=function(){
       ctx.beginPath();
       ctx.moveTo(this.coordinates[this.coordinates.length-1][0],this.coordinates[this.coordinates.length-1][1]);
       ctx.lineTo(this.x,this.y);
       ctx.strokeStyle="hsla("+this.hue+", 100%, "+this.brightness+"%, "+this.alpha+")";
       ctx.stroke()
   };

   function createParticles(x,y){
       var particleCount=30;
       while(particleCount--){
           particles.push(new Particle(x,y))
       }
   }

   function loop(){
       requestAnimFrame(loop);
       hue+=0.5;
       ctx.globalCompositeOperation="destination-out";
       ctx.fillStyle="rgba(0, 0, 0, 0.5)";
       ctx.fillRect(0,0,cw,ch);
       ctx.globalCompositeOperation="lighter";
       var i=fireworks.length;
       while(i--){
           fireworks[i].draw();fireworks[i].update(i)
       }
       var i=particles.length;
       while(i--){
           particles[i].draw();particles[i].update(i)
       }
       if(timerTick>=timerTotal){
           if(!mousedown){
               fireworks.push(new Firework(cw/2,ch,random(0,cw),random(0,ch/2)));
               timerTick=0
           }
       }
       else{ timerTick++}

       if(limiterTick>=limiterTotal){
               if(mousedown){
                   fireworks.push(new Firework(cw/2,ch,mx,my));
                   limiterTick=0
               }
       }
       else{ limiterTick++}
   }

   canvas.addEventListener("mousemove",function(e){
       mx=e.pageX-canvas.offsetLeft;
       my=e.pageY-canvas.offsetTop
   });
   canvas.addEventListener("mousedown",function(e){
       e.preventDefault();mousedown=true
   });
   canvas.addEventListener("mouseup",function(e){
       e.preventDefault();mousedown=false
   });
   window.onload=loop;
</script>
</body>
</html>

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