Legacy ImageMagick Discussions Archive

Hello, i have been searching all over the internet to find some information about ordered dithering, i found a lot of information about using ordered dither to reduce the colors to 2 colors but none about reducing colors to other amounts, so i was wondering if you could tell me how to use threshold maps. I have been looking at the source code but there are some values which for me is unknown (E.G. QuantumRange and QuantumScale)

The reason i want to know is that im updating a plugin for Paint.net that i made some month ago called Simulate Color Depth, and i would really like to have Ordered Dither in that plugin and all my results have been way too bright, dark or nearly the same pattern all over the image like it was a single shade of gray

I do understand if you dont want to tell me but it would be highly appreciated if you do and sorry if this is the wrong category

see http://www.imagemagick.org/Usage/quantize/#colors

Thanks, but i think i should have made myself more clear, it was the algorithm for ordered dithering i wanted to have a better understanding of but i eventually figured it out so it's working now, its based on the code in threshold.c so im wondering if it's ok i use it?

Regards Cookies

Look at the development page for ordered disther.

http://www.imagemagick.org/Usage/bugs/ordered-dither/

Note this uses a posterized set of colors. That is a mathematically generated set of colors.
It does NOT understand how to order dither an image to a given set of colors.

I would love to know how to do that, but have found little information on algorithms for that.

Thanks, i dont have any intention to make my paint.net plugin use a fixed palette (at least not yet) so it's fine for me

Also have a look at the 'Video Handling' section of IM Examples. Ordered dither is used to reduce the size of a GIF animation by removing the dither noise that the normal error-correction dither generates.