Canvas Pixel Manipulation

JavaScript performance comparison

Revision 18 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 jspixels = new Array(data.length * 4);
    var jspixels32 = new Array(data.length);
   
    var buf = new ArrayBuffer(imageData.data.length);
    var buf8 = new Uint8Array(buf);
    var data32 = new Uint32Array(buf);
   
    var pixels = new Int32Array(imageData.data.buffer);
};

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

Preparation code output

Test runner

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

    pixels[y * canvasWidth + x] = (255 << 24) | // alpha
    (value << 16) | // blue
    (value << 8) | // green
    value; // red
  }
}
pending…
32-bit Pixel Manipulation direct (o)
var ptr = 0;
for (var y = 0; y < canvasHeight; ++y) {
  var value = 0;
  for (var x = 0; x < canvasWidth; ++x) {
    var v = value & 0xff;
    pixels[ptr] = 0xFF000000 | (v * 0x010101);
    value += y;
    ptr++;
  }
}
pending…
jspixels
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;

    jspixels[index] = value; // red
    jspixels[++index] = value; // green
    jspixels[++index] = value; // blue
    jspixels[++index] = 255; // alpha
  }
}
pending…
jspixels32
for (var y = 0; y < canvasHeight; ++y) {
  for (var x = 0; x < canvasWidth; ++x) {
    var value = x * y & 0xff;

    jspixels32[y * canvasWidth + x] = (255 << 24) | // alpha
    (value << 16) | // blue
    (value << 8) | // green
    value; // red
  }
}
pending…

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