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);

Teardown JS


    ctx.putImageData(imageData, 0, 0);

Test cases

Test #1

Title *

Async

Code *

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
  }
}

imageData.data.set(buf8);
ctx.putImageData(imageData, 0, 0);

Test #2

Title *

Async

Code *

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

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

imageData.data.set(buf8);
ctx.putImageData(imageData, 0, 0);

Test #3

Title *

Async

Code *

var ch = canvasHeight-1;
var cw = canvasWidth-1;
var index = 0;
for (var y = 1; y < ch; ++y) {
  for (var x = 1; x < cw; ++x) {
    var value = x * y & 0xff;

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

imageData.data.set(buf8);
ctx.putImageData(imageData, 0, 0);

Test case details

Preparation Code

Test cases

Test #1

Test #2

Test #3