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<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> </head> <body> <canvas id="canvas" style="margin:0 auto;"> The current browser does not support Canvas, can replace the browser a try! </canvas> <script> window.onload = function(){ var canvas = document.getElementById(‘canvas‘); canvas.width = 1024; canvas.height = 768; if(canvas.getContext(‘2d‘)){ var context = canvas.getContext(‘2d‘); context.fillStyle = "#000"; context.fillRect(0,0,canvas.width,canvas.height) for(var i=0;i<200;i++){ var r = Math.random() * 10 + 10; var x = Math.random() * canvas.width; var y = Math.random() * canvas.height; var a = Math.random() * 360; drawStar(context , r , 2*r ,x , y , a ) } }else{ alert(‘当前游览器不支持Canvas，请更换游览器后再试！‘); } } // x,y是偏移量 rot 偏移量 function drawStar(cxt,r,R,x,y,rot){ cxt.beginPath(); for(var i=0;i<5;i++){ //假设大圆内径300 cxt.lineTo(Math.cos( (18+i*72 - rot) / 180 * Math.PI )*R+x, -Math.sin( (18+i*72 - rot) / 180 * Math.PI )*R+y); //假设小圆内径150 cxt.lineTo(Math.cos( (54+i*72 - rot) / 180 * Math.PI )*r+x, -Math.sin( (54+i*72 - rot) / 180 * Math.PI )*r+y); } cxt.closePath(); cxt.fillStyle = "#fb3"; cxt.strokeStyle = "fd5"; cxt.lineWidth = 3; cxt.lineJoin = "round" cxt.fill(); cxt.stroke(); } </script> </body> </html>
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原文地址：http://www.cnblogs.com/cynthia-wuqian/p/4978339.html
