Canvas rotate- 旋转

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>rotate</title>
</head>

<body>
    <canvas id='myCanvas' width='800' height='600'>
        your browser does not support canvas
    </canvas>
    <script type="text/javascript">
    var c = document.getElementById('myCanvas');
    var ctx = c.getContext('2d');
    ctx.beginPath();
    ctx.strokeStyle = '#000000';
    ctx.strokeRect(200, 50, 100, 50);
    ctx.rotate(0.25 * Math.PI);
    ctx.beginPath();
    ctx.strokeStyle = '#ff0000';
    ctx.strokeRect(200, 50, 100, 50);
    </script>
</body>

</html>

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>rotate</title>
</head>

<body>
    <canvas id='myCanvas' width='800' height='600'>
        your browser does not support canvas
    </canvas>
    <script type="text/javascript">
    var c = document.getElementById('myCanvas');
    var ctx = c.getContext('2d');
    ctx.beginPath();
    ctx.strokeStyle = '#000000';
    ctx.strokeRect(200, 50, 100, 50);
    ctx.translate(250,75);
    ctx.rotate(0.25 * Math.PI);
    ctx.translate(-250,-75);
    ctx.beginPath();
    ctx.strokeStyle = '#ff0000';
    ctx.strokeRect(200, 50, 100, 50);
    ctx.arc(250,75,2,0,2*Math.PI,true);
    ctx.stroke();
    </script>
</body>

</html>

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原文地址：https://www.cnblogs.com/stono/p/4670409.html