About clumping

When two spirals are mixed together, this situation will raise the inbetween pixel vlaues. When we allow the spirals to have large size, actually the inbetween areas will be hit a lot of times, not few times as I guessed. In my testing, the hitting usually reaches around 20 times. The highest hitting times once was 37 times in my testing. Thus, to make sure the inbetween pixels will be our next choice. The accumulation function has to be tricky. It has to drop very quickly from the center to the boundary to make sure the inbetween pixels are only raised a little values. It kind of avoids some clumpings. It turns out our guess is correct. The clumping ruins the tone matching. Right now I got very good tone matching based on PSNR measurement, better than the error diffusion method. But the structure similarity is not matched well and the visual effects are not very good either. Now I am adjustting the settings to want to get higher vlaues in both PSNR and MSSIM measurements. But right now I did not get that yet.

Another thing about clumping, after checking the results from the error diffusion, they have clumping too. But their clumping happens in vertical or diagonal direction. It seems in visualization the eyes can identify more quickly when two pixels are sticked together in a horizonal direction than the vertical ways. But right now I cannot avoid the horizonal situations.

the ramp image

MSSIMPSNR