Canvas Pixel Manipulation (v138)

Revision 138 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;
var len = data.length / 4;

for (var i = 0; i < len; i++) {

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

var c = 0;
var len = pixels.length;

for (var i = 0; i < len; i++) {

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

for (var i = 0; i < len; i++) {
  var alpha = pixels[i] & 0xFF000000;
  if (alpha !== 0) {
    c++;
  }
}
ready

Revisions

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