[magick-developers] about ImageMagick's dithering on a Hilbert-Peano curve

[Sam Hocevar]

On Fri, Aug 08, 2008, Anthony Thyssen wrote:

> Of course, It would be better to implement BOTH, and then let the user
> decide rather than just replacing one for another.

   That seems like a very reasonable 

> The most important thing being that a remainer method of distribution be
> used, so that any integer rounding is taken into account.  Your patch
> does not seem to take that into account. though that is also probably
> easily fixed.

   Yes. I was wary of propagating 100% of the error because I did not
know how the quantiser would react (I have seen ImageMagick choose weird
colours when dealing with restrictive palettes). But after thinking more
about it, I think it would do no harm. I'll update the patch.

> Then again there is a variety of ways of distributing the error
> than just the Floyd-Steinberg method.  It was just the first, and in
> many papers was not regarded as the best of this type.

   True (though I have shown in a recent paper that it was actually one
of the best of this type). I have also collected and implemented a lot
of different error diffusion methods for testing purposes, you may have
a look at them here: <http://libcaca.zoy.org/study/part3.html>. If you
believe one of them might be interesting for ImageMagick, let me know, I
should be able to provide reasonable patches for most of them.

Regards,
-- 
Sam.