1 | /* |
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2 | * libpipi Pathetic image processing interface library |
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3 | * Copyright (c) 2004-2008 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 library 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 | /* |
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16 | * median.c: median filter functions |
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17 | */ |
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18 | |
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19 | #include "config.h" |
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20 | |
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21 | #include <stdlib.h> |
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22 | #include <stdio.h> |
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23 | #include <string.h> |
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24 | #include <math.h> |
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25 | |
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26 | #include "pipi.h" |
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27 | #include "pipi_internals.h" |
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28 | |
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29 | static int cmpint(void const *i1, void const *i2) |
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30 | { |
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31 | return *(double const *)i1 < *(double const *)i2; |
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32 | } |
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33 | |
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34 | pipi_image_t *pipi_median(pipi_image_t *src, int radius) |
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35 | { |
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36 | return pipi_median_ext(src, radius, radius); |
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37 | } |
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38 | |
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39 | /* FIXME: this is in desperate want of optimisation. Here is what could |
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40 | * be done to improve the performance: |
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41 | * - prefetch the neighbourhood; most neighbours are the same as the |
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42 | * previous pixels. |
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43 | * - use a better sort algorithm; bubble sort is ridiculous |
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44 | * - even better, use state-of-the art median selection, ie. O(3n), for |
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45 | * most common combinations (9, 25, 49, 81). */ |
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46 | pipi_image_t *pipi_median_ext(pipi_image_t *src, int rx, int ry) |
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47 | { |
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48 | pipi_image_t *dst; |
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49 | pipi_pixels_t *srcp, *dstp; |
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50 | float *srcdata, *dstdata; |
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51 | double *list; |
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52 | int x, y, w, h, i, j, size, gray; |
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53 | |
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54 | w = src->w; |
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55 | h = src->h; |
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56 | size = (2 * rx + 1) * (2 * ry + 1); |
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57 | |
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58 | gray = (src->last_modified == PIPI_PIXELS_Y_F); |
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59 | |
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60 | srcp = gray ? pipi_getpixels(src, PIPI_PIXELS_Y_F) |
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61 | : pipi_getpixels(src, PIPI_PIXELS_RGBA_F); |
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62 | srcdata = (float *)srcp->pixels; |
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63 | |
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64 | dst = pipi_new(w, h); |
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65 | dstp = gray ? pipi_getpixels(dst, PIPI_PIXELS_Y_F) |
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66 | : pipi_getpixels(dst, PIPI_PIXELS_RGBA_F); |
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67 | dstdata = (float *)dstp->pixels; |
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68 | |
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69 | list = malloc(size * (gray ? 1 : 4) * sizeof(double)); |
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70 | |
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71 | for(y = 0; y < h; y++) |
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72 | { |
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73 | for(x = 0; x < w; x++) |
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74 | { |
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75 | double *parser = list; |
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76 | |
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77 | /* Make a list of neighbours */ |
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78 | for(j = -ry; j <= ry; j++) |
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79 | { |
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80 | int y2 = y + j; |
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81 | if(y2 < 0) y2 = h - 1 - ((-y2 - 1) % h); |
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82 | else if(y2 > 0) y2 = y2 % h; |
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83 | |
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84 | for(i = -rx; i <= rx; i++) |
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85 | { |
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86 | int x2 = x + i; |
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87 | if(x2 < 0) x2 = w - 1 - ((-x2 - 1) % w); |
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88 | else if(x2 > 0) x2 = x2 % w; |
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89 | |
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90 | if(gray) |
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91 | { |
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92 | *parser++ = srcdata[y2 * w + x2]; |
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93 | } |
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94 | else |
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95 | { |
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96 | parser[0] = srcdata[4 * (y2 * w + x2)]; |
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97 | parser[size * 1] = srcdata[4 * (y2 * w + x2) + 1]; |
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98 | parser[size * 2] = srcdata[4 * (y2 * w + x2) + 2]; |
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99 | parser[size * 3] = srcdata[4 * (y2 * w + x2) + 3]; |
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100 | parser++; |
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101 | } |
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102 | } |
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103 | } |
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104 | |
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105 | /* Sort the list */ |
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106 | qsort(list, size, sizeof(double), cmpint); |
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107 | if(!gray) |
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108 | { |
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109 | qsort(list + size, size, sizeof(double), cmpint); |
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110 | qsort(list + 2 * size, size, sizeof(double), cmpint); |
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111 | qsort(list + 3 * size, size, sizeof(double), cmpint); |
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112 | } |
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113 | |
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114 | /* Store the median value */ |
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115 | if(gray) |
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116 | { |
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117 | dstdata[y * w + x] = list[size / 2]; |
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118 | } |
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119 | else |
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120 | { |
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121 | dstdata[4 * (y * w + x)] = list[size / 2]; |
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122 | dstdata[4 * (y * w + x) + 1] = list[size / 2 + size * 1]; |
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123 | dstdata[4 * (y * w + x) + 2] = list[size / 2 + size * 2]; |
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124 | dstdata[4 * (y * w + x) + 3] = list[size / 2 + size * 3]; |
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125 | } |
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126 | } |
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127 | } |
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128 | |
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129 | return dst; |
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130 | } |
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131 | |
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