If you specify CRP_USERPALETTE in the iPalette parameter, pass the number of entries in your palette.iColors
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 CRP_USERPALETTE in the iPalette parameter, pass the number of entries in your palette.
If you specify CRP_OPTIMIZEDPALETTE in the iPalette parameter, you can use this parameter to limit the number of colors that the method maps in the optimized palette.