Canvas Pixel Manipulation

JavaScript performance comparison

Revision 28 of this test case created

Info

Tests two different methods of manipulating pixels using the canvas.

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);
  };

  Benchmark.prototype.teardown = function() {
    ctx.putImageData(imageData, 0, 0);
  };
</script>

Preparation code output

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Testing in unknown unknown
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…
32-bit Pixel Manipulation
 
for (var y = 0; y < canvasHeight; ++y) {
    for (var x = 0; x < canvasWidth; ++x) {
        var value = x * y & 0xff;

        data32[y * canvasWidth + x] =
            (255   << 24) |    // alpha
            (value << 16) |    // blue
            (value <<  8) |    // green
             value;            // red
    }
}

imageData.data.set(buf8);
 pending…
8-bit Typed 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;

        buf8[index]   = value;    // red
        buf8[++index] = value;    // green
        buf8[++index] = value;    // blue
        buf8[++index] = 255;      // alpha
    }
}

imageData.data.set(buf8);
 pending…

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