Using the 2D discrete Fourier transform to fix rainbows in manga on color eInk

An interesting application of the 2D DFT to manga on color eink Kaleido 3 with math theory explained! Kobo Colour images.

Most of the slides are based on the DFT chapter in Digital Image Processing: A Practical Approach by Nick Efford. I learned DFT to understand this algorithm.

I love how blur and rainbow fix are basically different masks over FFT space. Such a miniscule difference but such a large impact.