- /*
- * edd error diffusion displacement
- * Copyright (c) 2008 Sam Hocevar <sam@zoy.org>
- * All Rights Reserved
- *
- * $Id$
- *
- * This program is free software. It comes without any warranty, to
- * the extent permitted by applicable law. You can redistribute it
- * and/or modify it under the terms of the Do What The Fuck You Want
- * To Public License, Version 2, as published by Sam Hocevar. See
- * http://sam.zoy.org/wtfpl/COPYING for more details.
- */
-
- /* This program computes the Floyd-Steinberg error diffusion algorithm's
- * displacement on the given input image. Error diffusion displacement is
- * introduced in the paper "Reinstating Floyd-Steinberg: Improved Metrics
- * for Quality Assessment of Error Diffusion Algorithms.", ICISP 2008
- * Proceedings. Lecture Notes in Computer Science 5099 Springer 2008, ISBN
- * 978-3-540-69904-0.
- *
- * The resulting dx/dy values are usually around 0.16/0.26 for images that
- * are not entirely black and white. */
-
- #include "config.h"
- #include "common.h"
-
- #include <stdio.h>
- #include <stdlib.h>
- #include <string.h>
-
- #include <pipi.h>
-
- #define Z 3
-
- int main(int argc, char *argv[])
- {
- double sigma = 1.2, precision = 0.001, step = 2.;
- double best = 1., fx = -1., fy = -1., bfx = 0., bfy = 0.;
- double e, e0, e1;
- pipi_image_t *img, *gauss, *dither, *tmp;
- int dx, dy;
-
- if(argc < 2)
- {
- fprintf(stderr, "%s: too few arguments\n", argv[0]);
- fprintf(stderr, "Usage: %s <image>\n", argv[0]);
- return EXIT_FAILURE;
- }
-
- /* Load image, convert it to grayscale, dither it with Floyd-Steinberg */
- img = pipi_load(argv[1]);
- pipi_getpixels(img, PIPI_PIXELS_Y_F);
- gauss = pipi_gaussian_blur(img, sigma);
- dither = pipi_dither_floydsteinberg(img, PIPI_SCAN_RASTER);
- pipi_free(img);
-
- /* Compute the standard error */
- tmp = pipi_gaussian_blur(dither, sigma);
- e0 = pipi_measure_msd(gauss, tmp);
- pipi_free(tmp);
-
- /* Compute the fast error */
- tmp = pipi_gaussian_blur_ext(dither, sigma, sigma, 0.16, 0.26);
- e1 = pipi_measure_msd(gauss, tmp);
- pipi_free(tmp);
-
- /* Compute displacement */
- while(step > precision)
- {
- for(dy = 0; dy <= Z; dy++)
- for(dx = 0; dx <= Z; dx++)
- {
- tmp = pipi_gaussian_blur_ext(dither, sigma, sigma,
- fx + step * dx / Z,
- fy + step * dy / Z);
- e = pipi_measure_msd(gauss, tmp);
- pipi_free(tmp);
- if(e < best)
- {
- best = e;
- bfx = fx + step * dx / Z;
- bfy = fy + step * dy / Z;
- }
- }
-
- fx = bfx - step / Z;
- fy = bfy - step / Z;
- step = step * 2 / Z;
- }
-
- printf("E: %g E_fast: %g E_min: %g dx: %g dy: %g\n", e0, e1, best, fx, fy);
-
- pipi_free(dither);
- pipi_free(gauss);
-
- return 0;
- }
-
|