8-13 canvas专题-阶段练习二（下)

8-13 canvas专题-阶段练习二（下)-LMLPHP
 <!DOCTYPE html>

 <html lang="zh-cn">

 <head>

     <meta charset="UTF-8">

     <title>8-13 课堂演示</title>

 </head>

 <style type="text/css">

 </style>

 <body>

     <canvas id="canvas" width="800" height="600" >

             很抱歉，您的浏览器暂不支持HTML5的canvas

     </canvas>

     <script>

         var c=document.getElementById("canvas");

         var ctx=c.getContext("2d");

         ctx.lineWidth=5;

         ctx.strokeStyle="orange";

         ctx.fillStyle="red";

         var i=0;

         var j=100;

         var step=-1;

         function rotRect(){

             i++

             if(j==200){

                 step=-1

             }else if(j==1){

                 step=1

             }

             j+=step;

             ctx.save()

             ctx.clearRect(0,0,c.width,c.height)

             ctx.scale(j/100,j/100);

             ctx.translate(c.width/2,c.height/2);

             ctx.rotate(i*15*Math.PI/180)

             ctx.translate(-50,-50);

             ctx.strokeRect(0,0,100,100)

             ctx.fillRect(0,0,100,100)

             ctx.restore()

         }

         setInterval('rotRect()',10)

     </script>

 </body>

 </html>