HBMR algorithm discussion

[Iain]

I have done some amateur experiments with removing moire. See here:

Demosaicing Experiements

I’ve been playing with demosaicing, and since my shooting style seems to promote moire and aliasing I have been especially interested in reducing it. Here it is compared to LMMSE. LMMSE is on the left. [image] it works by first, demosaicing the image twice. On one the green channel is interpolated horizontally, the other vertically. Then the G-R and G-B is interpolated. This gives two very different moire patterns for each image. Then I choose which part of each image has the least chroma …

and:

Detect Moire Filter

I’ve just added a “Detect Moire” filter to Testing → Iain Fergusson. [Detect_moire] It’s a problem I’ve been trying to solve for a while and I was inspired to revisit it by the recent work done to combine demosaicers in Raw Therapee. It’s pretty good at detecting moire on low ISO images, high ISO images require a bit of fiddling to make sure noise is not causing false positives.

I don’t have the math background to immediately understand your PDF

My approach was always multi-channel. I think sampling theory makes undoing moiré from only a single channel’s data nearly impossible.

And I think the only way to undo it is to create a higher resolution image that can contain the frequencies you need to create. This is possible with the red and blue channels in a RAW file, because those are under-sampled, but the green channel is not so easy.