Canvas Pixel Manipulation

JavaScript performance comparison

Revision 90 of this test case created by mattdesl

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);
   
   
   
    function multiply1(pixels, rgba) {
            var r = ((rgba & 0xff000000) >>> 24),
                g = ((rgba & 0x00ff0000) >>> 16),
                b = ((rgba & 0x0000ff00) >>> 8),
                a = ((rgba & 0x000000ff)),
                len = pixels.length;
   
            for (var i=0; i<len; i+=4) {
                pixels[i] = pixels[i] * r / 255;
                pixels[i+1] = pixels[i+1] * g / 255;
                pixels[i+2] = pixels[i+2] * b / 255;
                pixels[i+3] = pixels[i+3] * a / 255;
            }
    }
   
    function multiply2(pixels, rgba) {
            var len = pixels.length,
                a1, a2, b1, b2, g1, g2, r1, r2,
                r, g, b, a,
                val;
   
            for (var i=0; i<len; i++) {
                val = pixels[i];
   
                a1 = ((val & 0xff000000) >>> 24);
                a2 = ((rgba & 0xff000000) >>> 24);
                b1 = ((val & 0x00ff0000) >>> 16);
                b2 = ((rgba & 0x00ff0000) >>> 16);
                g1 = ((val & 0x0000ff00) >>> 8);
                g2 = ((rgba & 0x0000ff00) >>> 8);
                r1 = ((val & 0x000000ff));
                r2 = ((rgba & 0x000000ff));
                r  = r1 * r2 / 255;
                g  = g1 * g2 / 255;
                b  = b1 * b2 / 255;
                a  = a1 * a2 / 255;
                   
                pixels[i] = (a << 24) | (b << 16) | (g << 8) | r;
            }
    }
};

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

Preparation code output

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Testing in unknown unknown
Test Ops/sec
32-bit Pixel Manipulation
multiply2(data32, 0xFF00FFFF);
imageData.data.set(buf8);
pending…
8-bit Pixel Manipulation
multiply1(data, 0xFF00FFFF);
pending…

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