[ubuntu-art] pngtobogl problem?

[Troy James Sobotka]

OK: ubuntu-logo-light.640x400.png (640x400, 4-bit colormap,
non-interlaced, 98.5 %).
OK: usplash-artwork.png (640x400, 4-bit colormap, non-interlaced,
98.5%).


That is the output I just tested on a couple of pngs that are 
failing in good old pngtobogl conversion.  Looks to me that
four bits is a sixteen color palette.  Anyone know what is going
wrong here?