Re: MMX speedup for Floyd Steinberg error diffusion

Terje wrote:

To do a mathematically perfect job I would start with a 5:5:5 (32 K) or
4:4:4 (4 K) table, with each entry being the start of a list of all the
possible palette entries for that entry:

By making each entry 16 bits wide, I could reserve the bottom 256
entries for colors that give a single possible result, and the remaining
values would be the start of pascal-style lists of possible entries,
stored as offsets into the same byte array.

I.e:

<code example snip>

Well, doing a crude implementation with a 4:4:4 array using
just one of 256 palette entries in each (no extra lists), I
ran some tests. On a nice slow Pentium, with a couple of test
images, the speed-up was maybe a factor of 50+ in display time.
With F-S dithering on, the image "looks" the same. With F-S
turned off, there was some obvious differences between the
table look up and the brute force search. The list of possible
entries version appears to be needed for an "optimum" result.
Somewhat interesting as I initially quantize to 4,096 bins, and
then reduce the palette using a pairwise clustering algorithm.

Vivek wrote:

In theory at least, 24 bit color GIFS are possible and could be
practical for static images...

Yup. Here is a link.

http://phil.ipal.org/tc.html

True-Color GIF Example

HTH,

Steve N.

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