Canvas Pixel Manipulation

JavaScript performance comparison

Revision 142 of this test case created by

Preparation code

<canvas id="canvas" height="256" width="256"></canvas>
      
<script>
Benchmark.prototype.setup = function() {
  var canvas = document.getElementById('canvas');
  var canvasWidth  = canvas.width;
  var canvasHeight = canvas.height;
  var ctx = canvas.getContext('2d');
  var imageData = ctx.getImageData(0, 0, canvasWidth, canvasHeight);
  
  var data = imageData.data;
  
  var buf = new ArrayBuffer(imageData.data.length);
  var buf8 = new Uint8ClampedArray(buf);
  var data32 = new Uint32Array(buf);
  
  // Determine whether Uint32 is little- or big-endian.
  data32[1] = 0x0a0b0c0d;
  
  var isLittleEndian = true;
  if (buf[4] === 0x0a && buf[5] === 0x0b && buf[6] === 0x0c &&
      buf[7] === 0x0d) {
      isLittleEndian = false;
  }

};

Benchmark.prototype.teardown = function() {
  ctx.putImageData(imageData, 0, 0);

};
</script>

Preparation code output

<canvas id="canvas" height="256" width="256"></canvas>

Test runner

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Testing in CCBot 2.0.0 / Other 0.0.0
Test Ops/sec
8-bit Pixel Manipulation
for (var y = 0; y < canvasHeight; ++y) {
    for (var x = 0; x < canvasWidth; ++x) {
        var index = (y * canvasWidth + x) * 4;

        var value = x * y & 0xff;

        data[index]   = value;    // red
        data[++index] = value;    // green
        data[++index] = value;    // blue
        data[++index] = 255;      // alpha
    }
}
pending…
not "detached"
for (var y = 0; y < canvasHeight; ++y) {
    for (var x = 0; x < canvasWidth; ++x) {
        var index = (y * canvasWidth + x) * 4;

        var value = x * y & 0xff;

        imageData.data[index]   = value;    // red
        imageData.data[++index] = value;    // green
        imageData.data[++index] = value;    // blue
        imageData.data[++index] = 255;      // alpha
    }
}
pending…

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