Canvas Pixel Manipulation (v27)

Revision 27 of this benchmark created by imaya on

Description

Tests two different methods of manipulating pixels using the canvas.

NOTE: Now takes endianness into account.

Preparation HTML

<canvas id="canvas" height="256" width="256"></canvas>

Setup

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);
    
    // Determine whether Uint32 is little- or big-endian.
    data32[1] = 0x0a0b0c0d;
    
    var isLittleEndian = true;
    if (buf[4] === 0x0a && buf[5] === 0x0b && buf[6] === 0x0c &&
        buf[7] === 0x0d) {
        isLittleEndian = false;
    }

Teardown


    ctx.putImageData(imageData, 0, 0);

Test runner

Ready to run.

Testing in
TestOps/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
    }
}
ready
32-bit Pixel Manipulation
if (isLittleEndian) {
    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
        }
    }
} else {
    for (y = 0; y < canvasHeight; ++y) {
        for (x = 0; x < canvasWidth; ++x) {
            value = x * y & 0xff;

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

imageData.data.set(buf8);
ready
8bit
var index = 0;
var value;

for (var y = 0; y < canvasHeight; ++y) {
    for (var x = 0; x < canvasWidth; ++x) {
        value = x * y & 0xff;

        data[index]     = value;    // red
        data[index + 1] = value;    // green
        data[index + 2] = value;    // blue
        data[index + 3] = 255;      // alpha
        index += 4;
    }
}
ready
32bit
var value;
var index = 0;

if (isLittleEndian) {
    for (var y = 0; y < canvasHeight; ++y) {
        index = y * canvasWidth;
        for (var x = 0; x < canvasWidth; ++x) {
            value = x * y & 0xff;

            data32[y * canvasWidth + x] =
              value |
              (value << 8) |
              (value << 16) |
              (255 << 24);
        }
    }
} else {
    for (var y = 0; y < canvasHeight; ++y) {
        index = y * canvasWidth;
        for (var x = 0; x < canvasWidth; ++x) {
            value = x * y & 0xff;

            data32[index + x] =
              (value << 24) |
              (value << 16) |
              (value << 8) |
              255;
        }
    }
}

imageData.data.set(buf8);
ready

Revisions

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