JohnDMcMaster/faxitron

Review histogram equalization

JohnDMcMaster opened this issue · 2 comments

JohnDMcMaster commented

Observation: when bad pixel replace is enabled on a mostly white image, the resulting equalized image is basically white. I suspect this is due to a hot pixel throwing off the dynamic range, but should confirm (maybe related to the corner issue)

When I use ImageMagick's dynamic algorithm (mine is not) it produces good images though. Ex: convert 2019-12-27_23_1.png ( +clone -equalize ) -average 2019-12-27_23_1_ei.png

Also consider switching to ImageMagick entirely if it produces nicer images in general

2019-12-27_23_1_e
Above: no BPR, faxitron equalization

2019-12-27_23_1_ei
Above: no BPR, ImageMagick equalization

2019-12-27_23_bpr_e
Above: BPR, faxitron equalization

2019-12-27_23_bpr_ei
Above: BPR, ImageMagick equalization

JohnDMcMaster commented

24bb001 adds some experimental modes. Notably "export FAXITRON_EQ_MODE=convert" will use ImageMagick. Default (0) is still old mode

JohnDMcMaster commented

There are two issues:
-Faulty bad pixel replacement which was skewing the histogram. This is fixed: #6
-We are using conventional histogram equalization

So the official resolution for now is:
-Correct your images properly to make sure there aren't bad pixels
-If you still get poor results, consider using dynamic histogram equalization (such as by FAXITRON_EQ_MODE=convert)