Is canvas getImageData method machine/browser dependent?

Question

A client required help with a program that extracts the dominant color of a product image.

I was able to quickly implement this in Javascript; the algorithm below o

Answer 1

Yes. This fact is exploited by canvas fingerprinting:

The same HTML5 Canvas element can produce exceptional pixels on a different web browsers, depending on the system on which it was executed.

This happens for several reasons: at the image format level — web browsers uses different image processing engines, export options, compression level, final images may got different hashes even if they are pixel-perfect; at the pixmap level — operating systems use different algorithms and settings for anti-aliasing and sub-pixel rendering. We don't know all the reasons, but we have already collected more than a thousand unique signatures.