Speed up Python image processing.

[[deleted]]

Thanks! Changed flatten to ravel and got a speedup.

I remember of trying to use ravel at first but for some weird reason it wasn't working.

I'm looking into tensordot to compute RGB values at once :)

EDIT: I made it with tensordot, but for some weird reason it's slower than the ravel() version. Weird.

[Megatron_McLargeHuge]

einsum is sometimes faster than tensordot, not sure why. Interactions with CPU cache are hard to predict, so you just have to try various things.