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<title>非零环绕原则</title>
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</canvas> <script> window.onload = function(){
var canvas = document.getElementById('canvas'); canvas.width = 1024;
canvas.height = 768; if(canvas.getContext('2d')){
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context.arc(400,400,300,0,Math.PI*2,false);
context.arc(400,400,150,0,Math.PI*2,true);
context.closePath(); context.fillStyle = "#058";
context.shadowColor = "gray";
context.shadowOffsetX = 10;
context.shadowOffsetY = 10;
context.shadowBlur = 10;
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