static void gradient_diagonal(RrSurface *sf, gint w, gint h);
static void gradient_crossdiagonal(RrSurface *sf, gint w, gint h);
static void gradient_pyramid(RrSurface *sf, gint inw, gint inh);
static void gradient_diagonal(RrSurface *sf, gint w, gint h);
static void gradient_crossdiagonal(RrSurface *sf, gint w, gint h);
static void gradient_pyramid(RrSurface *sf, gint inw, gint inh);