1 | /* |
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2 | * edd error diffusion displacement |
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3 | * Copyright (c) 2008 Sam Hocevar <sam@zoy.org> |
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4 | * All Rights Reserved |
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5 | * |
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6 | * $Id$ |
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7 | * |
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8 | * This program is free software. It comes without any warranty, to |
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9 | * the extent permitted by applicable law. You can redistribute it |
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10 | * and/or modify it under the terms of the Do What The Fuck You Want |
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11 | * To Public License, Version 2, as published by Sam Hocevar. See |
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12 | * http://sam.zoy.org/wtfpl/COPYING for more details. |
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13 | */ |
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14 | |
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15 | /* This program computes the Floyd-Steinberg error diffusion algorithm's |
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16 | * displacement on the given input image. Error diffusion displacement is |
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17 | * introduced in the paper "Reinstating Floyd-Steinberg: Improved Metrics |
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18 | * for Quality Assessment of Error Diffusion Algorithms.", ICISP 2008 |
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19 | * Proceedings. Lecture Notes in Computer Science 5099 Springer 2008, ISBN |
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20 | * 978-3-540-69904-0. |
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21 | * |
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22 | * The resulting dx/dy values are usually around 0.16/0.26 for images that |
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23 | * are not entirely black and white. */ |
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24 | |
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25 | #include "config.h" |
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26 | #include "common.h" |
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27 | |
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28 | #include <stdio.h> |
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29 | #include <stdlib.h> |
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30 | #include <string.h> |
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31 | |
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32 | #include <pipi.h> |
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33 | |
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34 | #define Z 3 |
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35 | |
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36 | int main(int argc, char *argv[]) |
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37 | { |
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38 | double sigma = 1.2, precision = 0.001, step = 2.; |
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39 | double best = 1., fx = -1., fy = -1., bfx = 0., bfy = 0.; |
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40 | double e, e0, e1; |
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41 | pipi_image_t *img, *gauss, *dither, *tmp; |
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42 | int dx, dy; |
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43 | |
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44 | if(argc < 2) |
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45 | { |
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46 | fprintf(stderr, "%s: too few arguments\n", argv[0]); |
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47 | fprintf(stderr, "Usage: %s <image>\n", argv[0]); |
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48 | return EXIT_FAILURE; |
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49 | } |
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50 | |
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51 | /* Load image, convert it to grayscale, dither it with Floyd-Steinberg */ |
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52 | img = pipi_load(argv[1]); |
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53 | pipi_getpixels(img, PIPI_PIXELS_Y_F); |
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54 | gauss = pipi_gaussian_blur(img, sigma); |
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55 | dither = pipi_dither_floydsteinberg(img, PIPI_SCAN_RASTER); |
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56 | pipi_free(img); |
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57 | |
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58 | /* Compute the standard error */ |
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59 | tmp = pipi_gaussian_blur(dither, sigma); |
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60 | e0 = pipi_measure_msd(gauss, tmp); |
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61 | pipi_free(tmp); |
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62 | |
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63 | /* Compute the fast error */ |
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64 | tmp = pipi_gaussian_blur_ext(dither, sigma, sigma, 0.16, 0.26); |
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65 | e1 = pipi_measure_msd(gauss, tmp); |
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66 | pipi_free(tmp); |
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67 | |
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68 | /* Compute displacement */ |
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69 | while(step > precision) |
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70 | { |
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71 | for(dy = 0; dy <= Z; dy++) |
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72 | for(dx = 0; dx <= Z; dx++) |
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73 | { |
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74 | tmp = pipi_gaussian_blur_ext(dither, sigma, sigma, |
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75 | fx + step * dx / Z, |
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76 | fy + step * dy / Z); |
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77 | e = pipi_measure_msd(gauss, tmp); |
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78 | pipi_free(tmp); |
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79 | if(e < best) |
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80 | { |
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81 | best = e; |
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82 | bfx = fx + step * dx / Z; |
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83 | bfy = fy + step * dy / Z; |
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84 | } |
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85 | } |
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86 | |
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87 | fx = bfx - step / Z; |
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88 | fy = bfy - step / Z; |
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89 | step = step * 2 / Z; |
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90 | } |
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91 | |
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92 | printf("E: %g E_fast: %g E_min: %g dx: %g dy: %g\n", e0, e1, best, fx, fy); |
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93 | |
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94 | pipi_free(dither); |
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95 | pipi_free(gauss); |
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96 | |
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97 | return 0; |
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98 | } |
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99 | |
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