I am working with images and Fourier transforms. I am trying to understand what might be causing some artifacts in my output image.
I am starting with a 512x512, RGB image of Lenna. I FFT the image, and run a low-pass filter on it. Unchanged for everything inside the circle, 0 for everything outside the circle. Here is what the mask looks like:
So far so good. When I inverse FFT back to an image, I get bright green artifacts:
These look out of place to me, what might be causing them? Is it the sharp cutoff in my filter? I would have guessed that would creating ringing artifacts, but nothing like a sharp color blob. Also why green only? It's not like there's a lot of green in the original.
I'm using numpy on python 2.7.6 in 64-bit Linux, if that matters.