How to change a picture to fail comparison algorithms? Is there a way to change a picture so it would fail to match against existing copy of the same picture on the big social networks such as Facebook, Twitter, Instagram, Tinder and others? Desired result should be as close as possible to the original.
It's dependent on the algorithm used for comparison, but if you have access to that algorithm, you can add small amounts of noise to pixels randomly until it misclassifies the image.

If you had deeper knowledge of the algorithm used, and it was differentiable, you could use gradient descent (ascent) to modify the image to increase the error of what was detected. This is the reverse of what you do when training image comparisons/classifiers which modify the weights to minimize the error.

But in short, if you dont have much knowledge of how the algorithm used works, I personally would try adding noise to pixels randomly, such that the image was still easily recognizable, but a decent amount of noise was added in.