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学了一点基础知识，感觉好神奇，全部练习代码

<html>

    <head>

        <meta http-equiv=Content-Type content="text/html;charset=utf-8">

        <title>Canvas element size:  x , Canvas drawing surface size:  x </title>

        <style>

            body {

                background: #dddddd;

            }

            #canvas {

                margin: 10px;

                padding: 10px;

                background: #ffffff;

                border: thin inset #aaaaaa;

            }

            #canvas2 {

                margin: 10px;

                padding: 10px;

                background: #ffffff;

                border: thin inset #aaaaaa;

                width: ;

                height: ;

            }

      </style>

    </head>

    <body>

        <canvas id='canvas' width='' height=''>

            Canvas not supported

        </canvas>

        <br/>

        .canvas有两个大小，一个是元素本身的大小，一个是绘图的大小.<br/>

        canvas默认绘图大小300,.设置CSS元素后，会将图像拉伸<br/>

        <canvas id='canvas2' class='canvas2' ><br/>

            Canvas not supported

        </canvas>

        <br/>

        .canvas的toDataURL(type,质量)返回图像路径，可以作为img的src显示。<br/>

        <img id='img2' src=""><br/>

        .canvas.getContext()方法返回canvasRenderingContext2D对象，属性和方法<br/>

        <a href='http://www.w3school.com.cn/jsref/dom_obj_canvasrenderingcontext2d.asp' target='_blank'>点这里！</a>

    </body>

    <SCRIPT TYPE="text/javascript">

        var canvas = document.getElementById('canvas'),

            context = canvas.getContext('2d');

        context.font = '38pt Arial';

        context.fillStyle = '#a1a1a1';//字体填充的颜色

        context.strokeStyle = 'red';//字体描边颜色

        context.fillText("Hello Canvas", canvas.width /  - ,

            canvas.height /  + );

        context.strokeText("Hello Canvas", canvas.width /  - ,

            canvas.height /  + );

        //alert(canvas.toDataURL("",1));

        var image = canvas.toDataURL("image/png",0.1);//返回图像

        document.getElementById("img2").src=image;//指定图像

        var canvas2 = document.getElementById('canvas2'),

            context2 = canvas2.getContext('2d');

        context2.font = '38pt Arial';

        context2.fillStyle = '#a1a1a1';//字体填充的颜色

        context2.strokeStyle = 'red';//字体描边颜色

        context2.fillText("Hello Canvas", canvas2.width /  - ,

            canvas2.height /  + );

        context2.strokeText("Hello Canvas", canvas2.width /  - ,

            canvas2.height /  + );

    </SCRIPT>

</html>