HTML5 Canvas 画图入门

HTML5 Canvas 画图入门，仅供学习參考
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>HTML5 移动Web开发指南</title>
    <style type="text/css">
        h1, h5
        {
            text-align: center;
        }
        canvas
        {
            float: left;
            margin: 10px;
            overflow: hidden;
        }
    </style>
    <script type="text/javascript" language="javascript">
        window.onload = function () {
            drawCanvas(0, 0, "canvase_01", "red", 200, 200);
            drawCanvas(0, 0, "canvase_02", "green", 200, 100);

            drawCanvas(0, 0, "canvase_05", "blank", 300, 60);
            drawCanvas(75, 60, "canvase_05", "gray", 150, 90);

            drawCanvas(0, 0, "canvase_06", "blank", 300, 50);
            drawCanvas(0, 50, "canvase_06", "red", 300, 50);
            drawCanvas(0, 100, "canvase_06", "#F8CB1C", 300, 50);

            drawCanvas(0, 0, "canvase_07", "green", 100, 150);
            drawCanvas(100, 0, "canvase_07", "white", 100, 150);
            drawCanvas(200, 0, "canvase_07", "red", 100, 150);

            drawRound("canvase_03", "blue", 75, true);
            drawRound("canvase_04", "yellow", 75, false);

            drawRound("canvase_08", "red", 75, true);
            drawRound("canvase_08", "yellow", 75, false);
        };


        /*
        * Canvas 画非圆图形測试
        * x:       图形的X轴開始坐标
        * y:       图形的Y轴開始坐标
        * id：     元素id
        * bgColor: 填充的背景颜色
        *    宽
        * height:  高
        */
        function drawCanvas(x, y, id, bgColor, width, height) {
            var canvas = document.getElementById(id);
            if (canvas != null && canvas != undefined) {
                var ctx = canvas.getContext("2d");
                ctx.fillStyle = bgColor;

                //第一个和第二个參数，代表開始坐标
                //第三个參数是图形的宽
                //第四个參数是图形的高
                ctx.fillRect(Number(x), Number(y), Number(width), Number(height));
            }
        }


        /*
        * Canvas 画圆測试
        * id：     元素id
        * bgColor: 填充的背景颜色
        * R：      圆半径
        * IsRound: 是否为正圆(true正圆、false 半圆)
        */
        function drawRound(id, bgColor, R, IsRound) {
            var canvas = document.getElementById(id);
            if (canvas != null && canvas != undefined) {
                var ctx = canvas.getContext("2d");
                ctx.fillStyle = bgColor;
                ctx.beginPath();

                var round = Math.PI;
                if (Boolean(IsRound))
                    round = Math.PI * 2;

                //第一个和第二个參数。代表圆心坐标
                //第三个參数是圆的半径
                //第四个參数代表圆周起始位置(0 起始位置。沿顺时针路线，各自是0.5 (正下方)。1 PI和1.5 PI(正上方)。为画饼图提供了扇形范围的根据)
                //第五个參数是弧长(Math.PI*1 半圆、Math.PI*2就是整个圆)
                ctx.arc(150, 75, Number(R), 0, round, true);

                ctx.closePath();
                ctx.fill();
            }
        }
    </script>
</head>
<body>
    <header>
        <section>
            <h1>
                HTML5 移动Web开发指南</h1>
        </section>
    </header>
    <fieldset>
        <legend>HTML5 新元素--Canvas画图元素</legend>
        <article>
            <section>
                <canvas id="canvase_01">
                 您的浏览器不支持Canvas元素！
                </canvas>
                <canvas id="canvase_02">
                 您的浏览器不支持Canvas元素！
                </canvas>
                <canvas id="canvase_03">
                 您的浏览器不支持Canvas元素！
                </canvas>
                <canvas id="canvase_04">
                您的浏览器不支持Canvas元素！

                </canvas>
                <canvas id="canvase_05">
                您的浏览器不支持Canvas元素。
                </canvas>
                <canvas id="canvase_06">
                您的浏览器不支持Canvas元素！

                </canvas>
                <canvas id="canvase_07">
                您的浏览器不支持Canvas元素！

                </canvas>
                <canvas id="canvase_08">
                您的浏览器不支持Canvas元素！
                </canvas>
            </section>
        </article>
    </fieldset>
    <footer>
        <section>
            <h5>
                <span style="font-family: Arial, Helvetica, sans-serif;">HTML5 新元素--Canvas画图元素</span>
            </h5>
        </section>
    </footer>
</body>
</html>
效果图：