千呼万唤 HTML 5 (10) - 画布（canvas）之转换

来源：互联网发布：软件安全性测试过程编辑：程序博客网时间：2024/06/06 08:36

原文地址：http://www.cnblogs.com/webabcd/archive/2012/02/22/2362505.html

作者：webabcd

介绍
HTML 5: 画布（canvas）之转换（转换画布的用户坐标系）

平移 | translate()
旋转 | rotate()
缩放 | scale()
矩阵转换 | transform(a, b, c, d, e, f)
矩阵转换 | setTransform(a, b, c, d, e, f)

示例
1、平移 | translate()
canvas/transform/translate.html

<!DOCTYPE HTML><html><head>    <title>平移</title></head><body>    <canvas id="canvas" width="400" height="400" style="background-color: rgb(222, 222, 222)">        您的浏览器不支持 canvas 标签    </canvas>    <br />    <button type="button" onclick="drawIt();">不断地点我看 Demo</button>    <button type="button" onclick="clearIt();">清除画布</button>    <script type="text/javascript">        var ctx = document.getElementById('canvas').getContext('2d');        var canvasX = 0;        var canvasY = 0;        var stepX = 20;        var stepY = 20;        function drawIt() {            if (canvasX == 0 && canvasY == 0)                ctx.strokeRect(0, 0, 100, 100);            canvasX += stepX;            canvasY += stepY;            /*             * context.translate(x, y) - 将当前的用户坐标系平移指定的距离             *   x - x 轴方向上需要平移的像素数             *   y - y 轴方向上需要平移的像素数             */            ctx.strokeStyle = "blue";            ctx.translate(stepX, stepY);            ctx.strokeRect(0, 0, 100, 100);        }        function clearIt() {            ctx.translate(-canvasX, -canvasY);            canvasX = 0;            canvasY = 0;            ctx.strokeStyle = "black";            ctx.clearRect(0, 0, 400, 400);        }    </script></body></html>

复制代码

2、旋转 | rotate()
canvas/transform/rotate.html

<!DOCTYPE HTML><html><head>    <title>旋转</title></head><body>    <canvas id="canvas" width="400" height="400" style="background-color: rgb(222, 222, 222)">        您的浏览器不支持 canvas 标签    </canvas>    <br />    <button type="button" onclick="drawIt();">不断地点我看 Demo</button>    <button type="button" onclick="clearIt();">清除画布</button>    <script type="text/javascript">        var ctx = document.getElementById('canvas').getContext('2d');        var canvasRadian = 0;        var stepRadian = 15 * Math.PI / 180;        function drawIt() {            if (canvasRadian == 0)                ctx.strokeRect(360, 0, 20, 60);            canvasRadian += stepRadian;            /*             * context.rotate(radian) - 将当前的用户坐标系旋转指定的弧度，顺时针为正值，逆时针为负值             *   radian - 弧度值             */            ctx.strokeStyle = "blue";            ctx.rotate(stepRadian);            ctx.strokeRect(360, 0, 20, 60);        }        function clearIt() {            ctx.rotate(-canvasRadian);            canvasRadian = 0;            ctx.strokeStyle = "black";            ctx.clearRect(0, 0, 400, 400);        }    </script></body></html>

复制代码

3、缩放 | scale()
canvas/transform/scale.html

<!DOCTYPE HTML><html><head>    <title>缩放</title></head><body>    <canvas id="canvas" width="400" height="400" style="background-color: rgb(222, 222, 222)">        您的浏览器不支持 canvas 标签    </canvas>    <br />    <button type="button" onclick="drawIt();">不断地点我看 Demo</button>    <button type="button" onclick="clearIt();">清除画布</button>    <script type="text/javascript">        var ctx = document.getElementById('canvas').getContext('2d');        var canvasScaleX = 1;        var canvasScaleY = 1;        var stepScaleX = 1.1;        var stepScaleY = 1.1;        function drawIt() {            if (canvasScaleX == 1 && canvasScaleY == 1)                ctx.strokeRect(0, 0, 60, 60);            canvasScaleX *= stepScaleX;            canvasScaleY *= stepScaleY;            /*             * context.scale(x, y) - 将当前的用户坐标系缩放指定的倍数             *   x - 水平方向上的缩放倍数             *   y - 垂直方向上的缩放倍数             */            ctx.strokeStyle = "blue";            ctx.scale(stepScaleX, stepScaleY);            ctx.strokeRect(0, 0, 60, 60);        }        function clearIt() {            ctx.scale(1 / canvasScaleX, 1 / canvasScaleY);            canvasScaleX = 1;            canvasScaleY = 1;            ctx.strokeStyle = "black";            ctx.clearRect(0, 0, 400, 400);        }    </script></body></html>

复制代码

4、矩阵转换 | transform(a, b, c, d, e, f)
canvas/transform/transform.html

<!DOCTYPE HTML><html><head>    <title>矩阵转换 | transform(a, b, c, d, e, f)</title></head><body>    <canvas id="canvas" width="400" height="400" style="background-color: rgb(222, 222, 222)">        您的浏览器不支持 canvas 标签    </canvas>    <br />    <button type="button" onclick="drawIt();">不断地点我看 Demo</button>    <button type="button" onclick="clearIt();">清除画布</button>    <script type="text/javascript">        var ctx = document.getElementById('canvas').getContext('2d');        var canvasScaleX = 1;        var canvasScaleY = 1;        var stepScaleX = 1.1;        var stepScaleY = 1.1;        function drawIt() {            if (canvasScaleX == 1 && canvasScaleY == 1)                ctx.strokeRect(0, 0, 60, 60);            canvasScaleX *= stepScaleX;            canvasScaleY *= stepScaleY;            /*             * context.transform(a, b, c, d, e, f) - 按指定的矩阵转换当前的用户坐标系             *   相当于：context.transform(M11, M12, M21, M22, OffsetX, OffsetY)             *             * 关于仿射矩阵参考：http://www.cnblogs.com/webabcd/archive/2008/11/03/1325150.html             *             *   |X|             |M11（默认值 1）      M21（默认值 0）       0|             *   |Y| = |x y 1| * |M12（默认值 0）      M22（默认值 1）       0|             *   |1|             |OffsetX（默认值 0）  OffsetY（默认值 0）   1|             *             *   X = x * M11 + y * M12 + OffsetX             *   Y = x * M21 + y * M22 + OffsetY             */            ctx.strokeStyle = "blue";            ctx.transform(stepScaleX, 0, 0, stepScaleY, 0, 0);            ctx.strokeRect(0, 0, 60, 60);        }        function clearIt() {            ctx.transform(1 / canvasScaleX, 0, 0, 1 / canvasScaleY, 0, 0);            canvasScaleX = 1;            canvasScaleY = 1;            ctx.strokeStyle = "black";            ctx.clearRect(0, 0, 400, 400);        }    </script></body></html>

复制代码

5、矩阵转换 | setTransform(a, b, c, d, e, f)
canvas/transform/setTransform.html

<!DOCTYPE HTML><html><head>    <title>矩阵转换 | setTransform(a, b, c, d, e, f)</title></head><body>    <canvas id="canvas" width="400" height="400" style="background-color: rgb(222, 222, 222)">        您的浏览器不支持 canvas 标签    </canvas>    <br />    <button type="button" onclick="drawIt();">Demo</button>    <button type="button" onclick="clearIt();">清除画布</button>    <script type="text/javascript">        var ctx = document.getElementById('canvas').getContext('2d');        function drawIt() {            ctx.strokeStyle = "red";            ctx.scale(2, 2);            ctx.strokeRect(0, 0, 60, 60);            /*             * context.setTransform(a, b, c, d, e, f) - 首先重置用户坐标系，然后再按指定的矩阵转换用户坐标系（translate, rotate, scale, transform 是针对当前用户坐标系做转换，而 setTransform 是针对重置后的用户坐标系做转换）             *   相当于：context.setTransform(M11, M12, M21, M22, OffsetX, OffsetY)             *             * 关于仿射矩阵参考：http://www.cnblogs.com/webabcd/archive/2008/11/03/1325150.html             *             *   |X|             |M11（默认值 1）      M21（默认值 0）       0|             *   |Y| = |x y 1| * |M12（默认值 0）      M22（默认值 1）       0|             *   |1|             |OffsetX（默认值 0）  OffsetY（默认值 0）   1|             *             *   X = x * M11 + y * M12 + OffsetX             *   Y = x * M21 + y * M22 + OffsetY             */            ctx.strokeStyle = "blue";            ctx.setTransform(1, 0, 0, 1, 0, 0);            ctx.strokeRect(0, 0, 60, 60);        }        function clearIt() {            ctx.clearRect(0, 0, 400, 400);        }    </script></body></html>

复制代码

OK
[源码下载]