I’m surprised anyone would be using an image-recognition algorithm that could be fooled by any 2D affine transformation and/or monotonic color transformation. The types of algorithm that are currently referred to as “machine learning” can already do much better than this, especially where you’re not overly concerned about false positives.
Still, any particular image-filtering algorithm is going to have ways it can be fooled, even if it takes special tools to do it, and if it’s a famous image (like the Tiananmen Square still), even a highly distorted copy will have the same effect since people know what the original looks like.
I wonder if the Great Firewall people considered better algorithms, and concluded that it wouldn’t stop anything that’s not being stopped already. And on a more paranoid level, I wonder if they do use better algorithms, not to censor images, but to detect people circumventing the weak censorship.
