-void image_filter_init(IMAGE *im, int domain, double bw, int filt_type, double filt_param, int opt_trace);
-/* im_draw.c */
-void image_show(IMAGE *im, int nxcell, int nycell, double densmin, double densmax, bool disp_scale);
-int image_paint(int dev, IMAGE *im, int xmin, int ymin, int nxcell, int nycell, double densmin, double densmax, bool disp_scale);
-int gs_image(GREYSCALE *gs, IMAGE *im, double densmin, double densmax, bool disp_scale);
-void paint_cscale(GREYSCALE *gs, int nx, int ny);
-GREYSCALE *gs_init(int dev, int xmin, int ymin, int nxcell, int nycell);
-void gs_pixel(GREYSCALE *gs, int x, int y, int gs_level);
-void gs_set_pos(GREYSCALE *gs, int x, int y);
-void gs_set_at_addr(GREYSCALE *gs, int gs_level);
-void gs_set_color_scale(void);
+double filter_spatial_response_calc(int filt_type, double x, double bw, double param, int n);
+double filter_spatial_response_analytic(int filt_type, double x, double bw, double param);
+double filter_frequency_response(int filt_type, double u, double bw, double param);
+double sinc(double x, double mult);
+double integral_abscos(double u, double w);
+