function ReduceColors(Bitmap: TBitmap; ColorReduction: TColorReduction; DitherMode: TDitherMode; ReductionBits: integer; CustomPalette: hPalette): TBitmap;

TBitmap ReduceColors(TBitmap Bitmap, TColorReduction ColorReduction, TDitherMode DitherMode, int ReductionBits, hPalette CustomPalette);