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<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <title>二进制雨</title></head><body><div style="color:red;text-align: center;font-size: 20px;">二进制雨</div><canvas id="myCanvas" width="1000px" height="600px" style="background-color: black;"></canvas><script> var draw=function(ctx,x,y,size){ this.ctx=ctx; this.x=x; this.y=y; this.size=size; var y1=this.y; this.drawText=function(){ var str=Math.ceil(Math.random()*10000).toString(2); var grd=this.ctx.createLinearGradient(this.x,this.y,this.x,this.y-this.ctx.measureText(str).width); grd.addColorStop(0,"#00FF00"); grd.addColorStop(1,"#004400"); this.ctx.fillStyle=grd; this.ctx.font=this.size+"px Arial"; for(var i=str.length-1;i>=0;i--) { this.ctx.fillText(str.charAt(i), this.x, y1-=15); } y1=this.y+=10; if(y1-720+this.ctx.measureText(str).width>0){ this.x=Math.ceil(Math.random()*1000); y1=this.y=Math.ceil(Math.random()*100); } } }; var rain=function(ctx,length){ this.length=length; this.ctx=ctx; var x=[]; var y=[]; var size=[]; var texts=[]; var i=0; for(;i<length;i++){ x[i]=Math.ceil(Math.random()*1000); y[i]=Math.ceil(Math.random()*500); size[i]=Math.ceil(Math.random()*15); texts[i]=new draw(this.ctx,x[i],y[i],size[i]); } this.run=function(){ ctx.clearRect(0,0,1000,600); for(var j=0;j<length;j++){ texts[j].drawText(); } }; }; var canvas=document.getElementById("myCanvas"); var ctx=canvas.getContext("2d"); var rain0=new rain(ctx,100); setInterval(rain0.run,50); </script></body></html> |
原文：http://www.cnblogs.com/startnow/p/5013383.html