Canvas-2D-Context-API-Primer/state_stack.html at master · rroa/Canvas-2D-Context-API-Primer · GitHub

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<!--
To change this template use Tools | Templates.
-->
<!DOCTYPE html>
<html>
<head>
    <title>Canvas 2D Context API Primer</title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=1024" />
    <meta name="apple-mobile-web-app-capable" content="yes" />

    <!--SCRIPTS-->
    <script type="text/javascript">
         /*
          # Context 2D API: scale
          The scale method modifies the transformation by multiplying the matrix by the specified factor.

          # Standard Definition.
          http://www.w3.org/html/wg/drafts/2dcontext/html5_canvas/#dom-context-2d-scale

          # Function signature
          void scale(unrestricted double x, unrestricted double y);

        */
        function draw(){
            // Get a reference to the canvas
            var canvas = document.getElementById('canvas');

            // Get a reference to the drawing context
            var ctx = canvas.getContext('2d');

            var rectWidth = 150;
            var rectHeight = 75;

            ctx.save();

            // save state 1
            ctx.translate(canvas.width / 2, canvas.height / 2);

            ctx.save();
            // save state 2
            ctx.rotate(Math.PI / 4);

            ctx.save();
            // save state 3
            ctx.scale(2, 2);

            ctx.fillStyle = 'blue';
            ctx.fillRect(rectWidth / -2, rectHeight / -2, rectWidth, rectHeight);

            ctx.restore();
            // restore state 3
            ctx.fillStyle = 'red';
            ctx.fillRect(rectWidth / -2, rectHeight / -2, rectWidth, rectHeight);

            ctx.restore();
            // restore state 2
            ctx.fillStyle = 'yellow';
            ctx.fillRect(rectWidth / -2, rectHeight / -2, rectWidth, rectHeight);

            ctx.restore();
            // restore state 1
            ctx.fillStyle = 'green';
            ctx.fillRect(rectWidth / -2, rectHeight / -2, rectWidth, rectHeight);
        }
    </script>
</head>
<body onload="draw();">
    <canvas id="canvas" width="350" height="400">
      This browser or document mode doesn't support canvas
    </canvas>
</body>
</html>