Sam Hocevar on wrote... | Dear developers, | | Each time I run "convert src.png -monochrome dest.png" and see the | result I want to cry. I have always wondered why ImageMagick was giving | Riemersma so much credit by using a dithering method (from the C/C++ | Users Journal) that was never peer-reviewed by people of the field and | gives so mediocre results. Parsing the image along a fractal curve is | elegant and interesting, but propagating the error along the very same | curve is nonsensical. Even Floyd-Steinberg's artifacts seem preferrable. | Is there a way to convince the team to use something else as the default | dithering method? | I have been pushing to add new dithering methods, including Floyd-Steinberg, though that is not regarded as a very good dithering method, it was just one of the first few methods. From what I have read there are many other simular methods (single pass processing) that produce a better results.
However from what I can see, a Riemersma, or hilbert curve dither, (IM is not exactly Riemersma, but a close variation on it), is better than a linear, one-pass dithering method, like Floyd-Steinberg Dither. However I do not want to get into any flame war about it. My own concerns with dithering was the psuedo-randomness that comes from the distribution of the error. That is a single pixel change causes a completely different pattern over all the parts of the image that follows. All error-correction dithers suffer from this, and it basically makes animations a pain to deal with. See some results in.. http://www.imagemagick.org/Usage/video/#gif It was because of this concern that I re-wrote the Order-Dither algorithm so that it can be used with colored images, and not just black and white. However it is limited to using specific color levels, rather that the 'best' color map. I know there is a algorithm that will allow ordered-dither to use a given color map, but have not found any information on that method, so have been unable to implement it. Basically IM is open to implement other dithering methods, or even any raster image processing algorithm. What is needed is someone with the time, the programming skills (C programming), and the knowledge to add new routines. What a new general dithering method becomes available, then the +/-dither option can then be replaced with something to select what type of general dithering method should be employed. You are welcome to add the new dither, and submit a patch, You can download the latest Subversion beta sources from the IM website, which you can compile and run directly from the source area (mail me for details, I'll be glad to help). When Cristy is satisified as to your skill I am sure he will then open the subversion repository to allow you to add changes and updates directly. I myself am currently very busy adding new Image Distortion methods, and Area Resampling improvements to IM. But am willing to help people add to IM. Anthony Thyssen ( System Programmer ) <[EMAIL PROTECTED]> ----------------------------------------------------------------------------- Are you a devious, plotting, unreliable madman? Ah, good, then you can be my most trusted minister. -- Terry Pratchett - "Interesting Times" ----------------------------------------------------------------------------- Anthony's Home is his Castle http://www.cit.gu.edu.au/~anthony/ _______________________________________________ Magick-developers mailing list Magick-developers@imagemagick.org http://studio.imagemagick.org/mailman/listinfo/magick-developers
