#define PROCESS_IMAGE( type ) \
        int process_image_##type(void *img, int width, int height ) \
        {                                                          \
                int x, y;                                              \
                                                               \
                for (y = 0; y < height; y++) {                         \
                        for (x = 0; x < width; x++) {                      \
                                type(img, x, y);               \
                        }                                                  \
                }                                                      \
                return 0 ; \
        }

        PROCESS_IMAGE( foo )
        PROCESS_IMAGE( bar )
        PROCESS_IMAGE( baz )