uColors

The number of colors in the palette. Pass 0 for to get the default (such as 256 for 8 bits per pixel). Otherwise, do one of the following:

If you specify CRF_USERPALETTE in the iPalette parameter, pass the number of entries in your palette.

If you specify CRF_OPTIMIZEDPALETTE in the iPalette parameter, you can use this parameter to limit the number of colors that the method maps in the optimized palette.