# 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>``

## Test runner

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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…

## Revisions

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