Update Barely made any progress. Been busy and exhausted. Incoming discussion.
Guided filter Besides getting it ready, I have realized that it is slow for normal use, a limitation of G’MIC scripting, among other factors. Radius 1-2 are very fast but larger radii are much slower. Without optimizing or compromising the code (or writing and compiling C++ code), I might decide to extend the core filter with an iterative (edge-preserving1) version.
1 Long term work in progress. Edge detection gradient_norm is surprisingly elegant, compared to other methods, but as I have noted in other posts, strong edges aren’t only brighter but also thicker. A map with lines with even brightness and thickness would be ideal for pixel weighting. There are other approaches to edge-preservation but they are difficult to understand and implement properly.
Local contrast This would depend on the guided filter, as do many filters on my to do list. Research on this isn’t done. I have much to learn. What I do have is a working filter that is conservative to the point where it behaves like a sharpener.
Sharpen Speaking of which, instead of including my LoG (Laplacian of Gaussian) filter, I have decided to make a new one using FFT.
Dehaze Sorry about hyping it up. The haze removal I want to do requires lots of elements to work individually and in tandem, a robust guided filter being one of them. Currently, it is last on my list of priorities. Original thread: Developing afre_dehaze.