canvas-blitting-sparse

JavaScript performance comparison

Test case created by Ilmari

Preparation code

<script>
  var c = document.createElement('canvas');
  c.width = c.height = 256;
  var ctx = c.getContext('2d');
  
  var framebuffer = ctx.getImageData(0, 0, 256, 256);
</script>

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Testing in unknown unknown
Test Ops/sec
fillRect
 
ctx.clearRect(0, 0, 256, 256);
for (var j = 0; j < 16; j++) {
 var xoff = Math.cos(j / 16 * Math.PI * 2) * 32 + 128;
 var yoff = Math.sin(j / 16 * Math.PI * 2) * 32 + 128;
 for (var i = 0; i < 256; i++) {
  var x = Math.cos(i / 256 * Math.PI * 2) * 64 + xoff;
  var y = Math.sin(i / 256 * Math.PI * 2) * 64 + yoff;
  ctx.fillRect(x, y, 1, 1);
 }
}
 pending…
putImageData
 
var px = framebuffer.data;
for (var i = 0; i < px.length; i++) {
 px[i] = 0;
}
for (var j = 0; j < 16; j++) {
 var xoff = Math.cos(j / 16 * Math.PI * 2) * 32 + 128;
 var yoff = Math.sin(j / 16 * Math.PI * 2) * 32 + 128;
 for (var i = 0; i < 256; i++) {
  var x = Math.cos(i / 256 * Math.PI * 2) * 64 + xoff;
  var y = Math.sin(i / 256 * Math.PI * 2) * 64 + yoff;
  var off = (y * 256 + x) * 4;
  px[off] = 0;
  px[off + 1] = 0;
  px[off + 2] = 0;
  px[off + 3] = 255;
 }
}
ctx.putImageData(framebuffer, 0, 0);
 pending…
putImageData with fresh buffer
 
ctx.clearRect(0, 0, 256, 256);
var framebufferi = ctx.getImageData(0, 0, 256, 256);
var px = framebufferi.data;
for (var j = 0; j < 16; j++) {
 var xoff = Math.cos(j / 16 * Math.PI * 2) * 32 + 128;
 var yoff = Math.sin(j / 16 * Math.PI * 2) * 32 + 128;
 for (var i = 0; i < 256; i++) {
  var x = Math.cos(i / 256 * Math.PI * 2) * 64 + xoff;
  var y = Math.sin(i / 256 * Math.PI * 2) * 64 + yoff;
  var off = (y * 256 + x) * 4;
  px[off] = 0;
  px[off + 1] = 0;
  px[off + 2] = 0;
  px[off + 3] = 255;
 }
}
ctx.putImageData(framebufferi, 0, 0);
 pending…

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