Canvas Pixel Manipulation

JavaScript performance comparison

Revision 82 of this test case created

Info

Tests two different methods of manipulating pixels using the canvas.

Preparation code

<canvas id="canvas" height="512" width="512"></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
draw rect
for (var y = 0; y < canvasHeight; ++y) {
  for (var x = 0; x < canvasWidth; ++x) {

    var value = x * y & 0xff;

    ctx.fillStyle = 'rgba(' + value + ',' + value + ',' + value + ',' + 255 + ')';
    ctx.fillRect(x, y, 1, 1);
  }
}
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…
put imagedata
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);
ctx.putImageData(imageData, 0, 0);
pending…

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