🚀 go-pugleaf

In article <24050@castle.ed.ac.uk> asr@castle.ed.ac.uk (Angus "Fluffy" Rae) writes:
[ description of color palette reduction algorithm deleted ]
>Can anyone point me at an algorithm for this sort of colourmap
>reduction? a) and b) above might be mutually exclusive - a fast routine
>that is pretty kludgy as far as colour selection goes would also be
>useful. I've heard the phrase "mean-cut" or something like it in
>reference to b).

The best paper I've seen on this is "Color Image Display with a Limited
Palette Size", Bouman and Orchard, Proceedings of the SPIE Visual
Communications and Image Processing Conference IV, SPIE Vol. 1199,
pp 522-533, 1989

This is basically the median split algorithm using statistical analysis
for each node to determine the direction and location of the split.
(you do have to find the principal eigenvalue of a 3x3 matrix, so have
your _Numerical Recipes_ handy).

I've gotten excellant results by combining this median split algorithm
with a couple of iterations of the Linde-Buzo-Grey algorithm and
Floyd-Steinberg dithering, but the LBG algorithm is quite slow.



Mike Jones