Some browsers (at least recent Chrome versions) automatically take
image metadata into account when drawing images into a canvas.
There seem to be no way to prevent that behavior, and the only
way to detect it seems to compare with a known image.

See: https://github.com/w3c/csswg-drafts/issues/4666
Solution adapted from: https://github.com/blueimp/JavaScript-Load-Image/commit/1e4df707821a0afcc11ea0720ee403b8759f3881