[Gimp-print-devel] New dither matrix

[Thomas T. <tt...@bi...>]

I built a new dither matrix program that is fast and gives good results.
It is in print/Matgen, including a 199x199 output matrix. Also in Matgen
(I know it shouldn't be there...) is a patched version of print-dither.c
that #includes the 199 size matrix.

Apologies for the large file, but generating it takes a few hours and
I'd like to save you that time.

Preliminary results: I _like_ the output with selecting ordered dither!
A light grey wedge seems much, much smoother than with random FS and
distribution of dots really is neat. Dark areas are a bit noisier though
than with Random FS, but no trace of this colored splotchyness (that
problem may have been solved by other changes though).

With the posted combination good print results can be obtained. A
white-to-black wedge has some problems in the dark area: the transition
from 'dark green' to 'black' (excuse the description) is not smooth: I
think because of the way the matrix is re-used.

In general, dark colors are a bit less smooth than light colors. But a
color like R211/G170/B74 looks better with ordered dither as the
distribution of cyan dots is much smoother.

Also, Random FS (in the patched version) seems to have some artefacts.
This time I printed a pattern of colored blocks. Random FS shows two of
these with aright hand edge that gets slighly darker down the page, and
there is a block (which is a dirty yellow) where 4 magenta and a cyan
pixel 'escaped' at the bottom. This may be the 'random' in random FS
though.

Finally, FS looks better on photographs because it has a sharpening
effect that is missing in ordered dithers.

I take the conclusion that FS is better for dark tints while ordered
dither now is better for light tints.


Thomas