Canvas Pixel Manipulation (v139)

Revision 139 of this benchmark created on

Description

Tests two different methods of manipulating pixels using the canvas.

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);
    
    var pixels = new Int32Array(imageData.data.buffer);

Teardown


    ctx.putImageData(imageData, 0, 0);

Test runner

Ready to run.

Testing in
TestOps/sec
8-bit read alpha
var c = 0;

for (var y = 0; y < canvasHeight; ++y) {
  for (var x = 0; x < canvasWidth; ++x) {
    var i = (y * canvasWidth + x) * 4;

    var alpha = data[i + 3];
    if (alpha !== 0) {
      c++;
    }
  }
}
ready
32-bit read alpha
var c = 0;

for (var y = 0; y < canvasHeight; ++y) {
  for (var x = 0; x < canvasWidth; ++x) {
    var i = y * canvasWidth + x;

    var alpha = (pixels[i] >> 24) & 0xFF;
    if (alpha !== 0) {
      c++;
    }
  }
}
ready
32-bit read alpha flat
var c = 0;

for (var y = 0; y < canvasHeight; ++y) {
  for (var x = 0; x < canvasWidth; ++x) {
    var i = y * canvasWidth + x;
    var alpha = pixels[i] & 0xFF000000;
    if (alpha !== 0) {
      c++;
    }
  }
}
ready

Revisions

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