HTML5 画布 Canvas
来源：程序员人生 发布时间：2014-10-06 08:00:00 阅读次数：4313次
利用html5的canvas元素使用 JavaScript 在网页上绘制图像。
通过规定尺寸、颜色和位置，来绘制一个圆：
<!DOCTYPE htma>
<html>
<body>
<canvas id="myCanvas" width="200" height="100" style="border:1px solid #3CF;">
Your browser does not support the canvers element.
</canvas>
<script type="text/javascript">
var c=document.getElementById("myCanvas");
var cxt=c.getContext("2d");
cxt.fillStyle="#3CF";
cxt.beginPath();
cxt.arc(70,18,15,0,Math.PI*2,true);
cxt.closePath();
cxt.fill();
</script>
</body>
</html>
通过指定从何处开始，在何处结束，来绘制一条线
<!DOCTYPE HTML>
<html>
<body>
<canvas id="myCanvas" width="200" height="100" style="border:1px solid #c3c3c3;">
Your browser does not support the canvas element.
</canvas>
<script type="text/javascript">
var c=document.getElementById("myCanvas");
var cxt=c.getContext("2d");
cxt.moveTo(10,10);
cxt.lineTo(150,50);
cxt.lineTo(10,50);
cxt.stroke();
</script>
</body>
</html>
使用您指定的颜色来绘制渐变背景
<!DOCTYPE htma>
<html>
<body>
<canvas id="myCanvas" width="200" height="100" style="border:4px solid #3CF;">
Your browser does not support the canvers element.
</canvas>
<script type="text/javascript">
var c=document.getElementById("myCanvas");
var cxt=c.getContext("2d");
var grd=cxt.createLinearGradient(0,0,175,50);
grd.addColorStop(0,"#FF0000");
grd.addColorStop(1,"#00FF00");
cxt.fillStyle=grd;
cxt.fillRect(0,0,175,50);
</script>
</body>
</html>
把一幅图像放置到画布上
<!DOCTYPE HTML>
<html>
<body>
<canvas id="myCanvas" width="200" height="100" style="border:1px solid #c3c3c3;">
Your browser does not support the canvas element.
</canvas>
<script type="text/javascript">
var c=document.getElementById("myCanvas");
var cxt=c.getContext("2d");
var img=new Image()
img.src="/i/eg_flower.png"
cxt.drawImage(img,0,0);
</script>
</body>
</html>
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