chrome/test/data/third_party/kraken/hosted/explanations/gaussian-blur.html

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  32
  33 <title>Kraken JavaScript Benchmark: Gaussian Blur</title>
  34 <link rel="stylesheet" href="../kraken.css">
  35 <script>
  36
  37 </script>
  38 <style> #display { border: 5px solid rgb(0,0,50);}</style>
  39 </head>
  40
  41 <body>
  42 <div id="content">
  43 <h2>Kraken JavaScript Benchmark: Gaussian Blur</h2>
  44 <div id="results">
  45     <p>This benchmark performs a <a href="http://en.wikipedia.org/wiki/Gaussian_blur">Gaussian blur</a> on a photo.</p>
  46     <p><small>Photo courtesy <a href="http://www.flickr.com/photos/katclay/4296523922/in/photostream/">Kat Clay</a> from Flickr</small>.</p>
  47     <img id="image" src="squid.png" width="400" height="267">
  48     <canvas id="canvas" width="400" height="267"></canvas>
  49     <script>
  50       var sigma = 10; // radius
  51       var kernel, kernelSize, kernelSum;
  52       buildKernel();
  53
  54       try {
  55         // Opera createImageData fix
  56         if (!("createImageData" in CanvasRenderingContext2D.prototype)) {
  57           CanvasRenderingContext2D.prototype.createImageData = function(sw,sh) { return this.getImageData(0,0,sw,sh); }
  58         }
  59       } catch(e) {}
  60
  61       function buildKernel() {
  62         var ss = sigma * sigma;
  63         var factor = 2 * Math.PI * ss;
  64         kernel = [];
  65         kernel.push([]);
  66         var i = 0, j;
  67         do {
  68             var g = Math.exp(-(i * i) / (2 * ss)) / factor;
  69             if (g < 1e-3) break;
  70             kernel[0].push(g);
  71             ++i;
  72         } while (i < 7);
  73         kernelSize = i;
  74         for (j = 1; j < kernelSize; ++j) {
  75             kernel.push([]);
  76             for (i = 0; i < kernelSize; ++i) {
  77                 var g = Math.exp(-(i * i + j * j) / (2 * ss)) / factor;
  78                 kernel[j].push(g);
  79             }
  80         }
  81         kernelSum = 0;
  82         for (j = 1 - kernelSize; j < kernelSize; ++j) {
  83             for (i = 1 - kernelSize; i < kernelSize; ++i) {
  84                 kernelSum += kernel[Math.abs(j)][Math.abs(i)];
  85             }
  86         }
  87       }
  88
  89       function blurTest() {
  90         var results = document.getElementById('blur-result');
  91         results.innerHTML = "Running test...";
  92
  93         window.setTimeout(function() {
  94           var canvas = document.getElementById('canvas');
  95           var ctx = canvas.getContext('2d');
  96           var img = document.getElementById('image')
  97           ctx.drawImage(img, 0, 0, img.width, img.height);
  98
  99           var imgData = ctx.getImageData(0, 0, canvas.width, canvas.height);
 100           var width = imgData.width, height = imgData.height;
 101           var data = imgData.data;
 102
 103           var len = data.length;
 104           var startTime = (new Date()).getTime();
 105
 106           for (var y = 0; y < height; ++y) {
 107             for (var x = 0; x < width; ++x) {
 108               var r = 0, g = 0, b = 0, a = 0;
 109               for (j = 1 - kernelSize; j < kernelSize; ++j) {
 110                 if (y + j < 0 || y + j >= height) continue;
 111                 for (i = 1 - kernelSize; i < kernelSize; ++i) {
 112                   if (x + i < 0 || x + i >= width) continue;
 113                   r += data[4 * ((y + j) * width + (x + i)) + 0] * kernel[Math.abs(j)][Math.abs(i)];
 114                   g += data[4 * ((y + j) * width + (x + i)) + 1] * kernel[Math.abs(j)][Math.abs(i)];
 115                   b += data[4 * ((y + j) * width + (x + i)) + 2] * kernel[Math.abs(j)][Math.abs(i)];
 116                   a += data[4 * ((y + j) * width + (x + i)) + 3] * kernel[Math.abs(j)][Math.abs(i)];
 117                 }
 118               }
 119               data[4 * (y * width + x) + 0] = r / kernelSum;
 120               data[4 * (y * width + x) + 1] = g / kernelSum;
 121               data[4 * (y * width + x) + 2] = b / kernelSum;
 122               data[4 * (y * width + x) + 3] = a / kernelSum;
 123             }
 124           }
 125           var finishTime = Date.now() - startTime;
 126           for (var i = 0; i < data.length; i++) {
 127               imgData.data[i] = data[i];
 128           }
 129           //imgData.data = data;
 130           ctx.putImageData(imgData, 0, 0);
 131           results.innerHTML = "Finished: " + finishTime + "ms";
 132         }, 10);
 133       }
 134     </script>
 135     <p><input type="button" value="Blur Test" onclick="blurTest();">&nbsp;<span id="blur-result"></span></p>
 136 </div>
 137 </div>
 138 </body>
 139 </html>