Kind of smudging effects

I am not sure if this is what are called smearing effects. But for me, it smudges the images. It did not do a good job for images with textures.

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

Some experiences

I tried the regular mask by using the same process. It turns out the regular mask will bring more artefacts than the spiral mask. In visualization, the same function will have similar effects. The differences are in different patterns introduced by different masks.

I also tried the floating points to store the values. Right now it gives more control for each step, but I cannot say what the other advantages are.

Right now it seems the limit of the size of the mask has a great effect on ruining tone.

The size of the mask has some influence in visual effects.

Performance: 512 by 512 takes 113 seconds.

I am going to put the tone down and try to find some interesting patterns from our method. Right now how to control patterns seems a mystry.

A few steps for running

The left side has 100 value in intensity and the right side has 200 value.

2000 stipples
3000 stipples
5000 stipples10000stipples
final

Strange effects

using the regular mask

using the spiral mask

A little better than the Pang's method in tone

Worse than the Ostromoukhov's mehtod and the error diffusion in tone match



The MSSIM comparison by 2003 Zhou Wang(matlab codes from their page)

http://www.ece.uwaterloo.ca/~z70wang/research/ssim/
The PSNR comparison(matlab codes from matlab central)

http://www.mathworks.com/matlabcentral/fileexchange/135
Use the Gaussian filter first for both images(11 by 11 window)

Measurement for halftoning

Do not know how they display the radially averaged power spectrum as the paper.

grayness = 0.75 copy the image from the paper and calculate it again.

grayness = 192
MSSIM to measure the structure simliarity

For(1-*) group
For(2-*)group
For(3-*)group

PSNR measurement for tone similariy

For(1-*) group
For(2-*) group
For(3-*) group
(01-cat)
(02-cat)
(03-cat)
(01-tree)
(02-tree)
(03-tree)
(01-a1)
(02-a1)
(03-a1)