fade_interpolate (3) - Linux Man Pages
fade_interpolate: Calculates a new palette interpolated between two others. Allegro game programming library.
fade_interpolate - Calculates a new palette interpolated between two others. Allegro game programming library.
void fade_interpolate(const PALETTE source, const PALETTE dest,
PALETTE output, int pos, int from, int to);
Calculates a temporary palette part way between source and dest,
returning it in the output parameter. The position between the two
extremes is specified by the pos value: 0 returns an exact copy of
source, 64 returns dest, 32 returns a palette half way between the two,
etc. This routine only affects colors between from and to (inclusive:
pass 0 and 255 to interpolate the entire palette).