this is more of a dcraw question than a libdraw, but I am hoping someone can help anyway.
I was wondering if somebody can post a sample image with 2x2 mesh or maze that was noted in dcraw manual that may happen. I recently tried to port dcraw to plan9. After making a few code changes, I was able to compile it. It works ok except when I use the AHD option where I get some dot patterns. I am still trying to trouble shoot it, but I was thinking if I new what a 2x2 mesh or maze look like it would help me in the process.
I have sample image here https://www.flickr.com/gp/uberclacker/o36832 this was using
dcraw -q 3 IMGPXXX.PEF
I seem to get a different pattern depending on what dcraw option I choose. The only thing common is that AHD is the interpolation method used. Using the same options in the linux version did not show any such pattern.
Any thoughts would be helpful.
Here is the sample of AHD
Here is the sample of AHD maze: https://picturecode.cachefly.net/photoninja/images/demosaic_before.jpg
Your blue dot artifacts are very different from that.
-- Alex Tutubalin @LibRaw LLC