For the past few days I have been writing a small application called DT2GIF (Datatype to GIF).
As input it will accept any image file supported by picture datatypes and it will quantize and output an 8bit GIF.
For Color Quantizing (Color Reduction) it used the Neuquant Algorithm. The results using the algorithm are excellent.
There's an Amiga OS3 binary of PNGNQ that uses the same Neuquant Code to quantize 32bit RGBA to 8bit PNG. So I used it to convert the two 32bit icon images.
One the left of the screenshot is the original image and on the right of each is the 8bit quantized image with "_nq8.png" appended to the filename. How is the quality?
My DT2GIF uses the same Neuquant Code so I know the code works. But the difficulty is getting the NQ Colormap and Indexes into what our Datatypes can deal with.
This is the closest I've been to Real Color Quantizing in the last 6 months! I believe I will get it to work after several more long hours of experimenting with it.