gdImageContrast  4840 gd/gd.c        	if (gdImageContrast(im_src, (int)contrast) == 1) {
gdImageContrast   662 gd/libgd/gd.h  int gdImageContrast(gdImagePtr src, double contrast);
gdImageContrast    30 gd/libgd/gd_compat.h int gdImageContrast(gdImagePtr src, double contrast);