cccooommmbbbiiinnneeesss pppgggmmm___rrreeeaaadddpppgggmmmiiinnniiittt((())), pppgggmmm___aaallllllooocccaaarrrrrraaayyy((())) and pppgggmmm___rrreeeaaadddpppgggmmmrrrooowww((())).
void pgm_writepgminit( FILE* fp, int cols, int rows, gray maxval, int