Calculates a new palette interpolated between two others. allegro game programming library.
#include <allegro.h>
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).
fade_in(3alleg4), fade_out(3alleg4), fade_from(3alleg4)