I've never liked that the colors resulting from GIMP's Posterize filter are somewhat random and do not correspond to the colors in the original image. It is also somewhat limited in that the number of resulting RGB colors must be a power of two (e.g., if Levels is "3" then the result has 8 colors, if "5" then 32 colors result, etc.).

Converting the image to Indexed Mode overcomes these limitations, but the entire image must be converted (not just the current layer, or the selected region of the current layer). Nonetheless, I often found myself performing a work-around of dragging a layer to the Toolbox, converting it to Indexed Mode, and then dragging it back.

I finally broke down and wrote a script which automates this task, as well as providing a couple of nice options for smoothing the edges between color transitions. The script does not do anything particularly special but it does seem to be well-behaved and I am basically happy with it (though a better name might be considered; too bad posterize is already taken ).

BEFORE:


AFTER:


The new function is added to the Colors menu and the command is named "Quantize". The script is described on my Chiselapp WIKI and a link to the download file is provided therein.

Any bug reports would be welcome.

cool, i also hate the result of the standard filter as its limitations for the number of colors.

I remember you wrote another "posterize" script somehow similar except that each color was in its own layer, i found that really useful for edit . But i lost it and i can't find on chiselapp do you still have it somewhere?

And... will work with gimp 2.7.3 ?

I recall a script for decomposing Indexed images to separate layers, but it is over five years old and in dire need of updating and migrating to my "official" repository (maybe I will get around to it next weekend).


It should, though I've not tested it.

Exact that,"decomposing Indexed images " was the technical process but the input, the image could be also RGB/RGBA
and it was a option to reconvert back image mode to rgb, so i somehow seen as a filter to posterize with greater control on the number of colors and, for further edit ,the convenience to have each color on its own layer

The only error i get in 2.7.3 is gimp-selection-load should be gimp-image-select-item
The filter works nice though.

Thanks Saulgoode.

I have updated the script to correct the mishandling of the alpha channel (avoiding the coercion of partially transparent colors to either 100% opaque or 100% transparent). This is an important fix and if you are using the script, I would recommend updating to latest version.

http://chiselapp.com/user/saulgoode/repository/script-fu/wiki?name=sg-quantize

Somehow missed this one; thanks Saul. I do look forward to trying this one (maybe my Legos will be better now; lol). Much need imo; Posterize really is lacking. Maybe the folks who wrote Cartoonize could use your algorithm instead of Posterize too.

sg-

You must have missed my post last year:
http://gimpchat.com/viewtopic.php?f=9&t ... 5449#p5449

-Rob A>

I didn't see or recall that either Rob, and I actually posted earlier on that thread. lol

I used the frog from the GIMP game post. I played with the settings and this one is the one I like best. Nice filter!

I like the filter too Saul. Thanks!!!

Liana

Indeed I had. Your palette selection and dithering options are interesting -- and I can see where they might be useful in cartography -- nonetheless I think I'll leave my script in its current state. I just feel it is more suitable to my needs.

@lianam, those are very nice. I particularly like the chicken picture.

I just wanted to point it out - nothing like having choice!

-Rob A>

they all look great!

A little comparison of different filters. All default or minimal changes except the G'mic...had to mess with it to get a decent picture.


oops, forgot default Quantize filter!

and Robs indexed poster script at default settings.