message: Optimal performance & cosmetic
diff: export default function trimCanvas(canvas)
  {
  // https://gist.github.com/remy/784508
  +
  + let width = canvas.width;
  + let height = canvas.height;
  +
  const context = canvas.getContext('2d');
  - const pixels = context.getImageData(0, 0, canvas.width, canvas.height);
  - const l = pixels.data.length;
  + const imageData = context.getImageData(0, 0, width, height);
  + const pixels = imageData.data;
  + const len = pixels.length;
  +
  const bound = {
  top: null,
  left: null,
  @@ -23,12 +29,12 @@ export default function trimCanvas(canvas)
  let x;
  let y;
  - for (i = 0; i < l; i += 4)
  + for (i = 0; i < len; i += 4)
  {
  - if (pixels.data[i + 3] !== 0)
  + if (pixels[i + 3] !== 0)
  {
  - x = (i / 4) % canvas.width;
  - y = ~~((i / 4) / canvas.width);
  + x = (i / 4) % width;
  + y = ~~((i / 4) / width);
  if (bound.top === null)
  {
  @@ -64,8 +70,9 @@ export default function trimCanvas(canvas)
  }
  }
  - const height = bound.bottom - bound.top + 1;
  - const width = bound.right - bound.left;
  + width = bound.right - bound.left;
  + height = bound.bottom - bound.top + 1;
  +
  const data = context.getImageData(bound.left, bound.top, width, height);
  return {
  