ham_convert released in the Version 1.8.8.

Changes:

* HAM6/HAM8: fixed a bug when converter tended to use HAM modify commands even if it could use a base-color instead (if set and modify produce the same color). If the output image still has background mostly encoded using modify operations most likely the exact background color isn’t present in the palette. NeuQuant and Wu often produce slightly altered background color. You can try updating the palette manually (using built-in palette editor or editing pal file in text editor) or switching color quantizer to Median Cut (keep in mind that it’s not as advanced as Neuquant or Wu and it may decrease quality).
*HAM6: extra ham6 palette optimization can now optionally check all possible 4096 colors.
*Added Median Cut quantizer to the Amiga modes as an alternative to NeuQuant and Wu.
*Various gui fixes and tweaks.

http://mrsebe.bplaced.net/blog/wordpress/?p=1559