第三讲:动态画圆

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<html><head><title>初识canvas</title><script src="../js/jscex.jscexRequire.min.js" type="text/javascript"></script></head><body><canvas id="mc" width="900px" height="440px" style="border:1px solid #c3c3c3;background-color:#fff;border-radius:10px;"></canvas><script type="text/javascript">var canvas = document.getElementById('mc');var ctx = canvas.getContext('2d');var x = 150;var y = 150;var r = 100;//画出指定的图像var somethingAsync = eval(Jscex.compile("async",function(){ctx.moveTo(x - r,y);for(var i = x - r ; i< x+r+1;i++){$await(Jscex.Async.sleep(50));var tempY = Math.pow(r*r-(x-i)*(x-i),1/2);ctx.lineTo(i,y+tempY);ctx.stroke();}ctx.moveTo(x-r,y);for(var i = x - r ; i< x+r+1;i++){$await(Jscex.Async.sleep(50));var tempY = Math.pow(r*r-(x-i)*(x-i),1/2);ctx.lineTo(i,y-tempY);ctx.stroke();}}))somethingAsync().start();</script></body></html>

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