1 | /* |
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2 | * libpipi Pathetic image processing interface library |
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3 | * Copyright (c) 2004-2009 Sam Hocevar <sam@hocevar.net> |
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4 | * All Rights Reserved |
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5 | * |
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6 | * $Id: bresenham.c 4691 2010-10-16 21:52:45Z sam $ |
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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 | * bresenham.c: Bresenham image resizing 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 <string.h> |
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23 | |
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24 | #include "pipi.h" |
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25 | #include "pipi_internals.h" |
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26 | |
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27 | /* This is Bresenham resizing. I rediscovered it independently but it was |
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28 | * actually first described in 1995 by Tim Kientzle in "Scaling Bitmaps |
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29 | * with Bresenham". */ |
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30 | |
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31 | /* FIXME: the algorithm does not handle alpha components properly. Resulting |
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32 | * alpha should be the mean alpha value of the neightbouring pixels, but |
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33 | * the colour components should be weighted with the alpha value. */ |
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34 | pipi_image_t *pipi_resize(pipi_image_t *src, int w, int h) |
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35 | { |
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36 | float *srcdata, *dstdata, *aline, *line; |
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37 | pipi_image_t *dst; |
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38 | pipi_pixels_t *srcp, *dstp; |
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39 | int x, y, x0, y0, sw, dw, sh, dh, remy; |
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40 | float invswsh; |
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41 | |
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42 | srcp = pipi_get_pixels(src, PIPI_PIXELS_RGBA_F32); |
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43 | srcdata = (float *)srcp->pixels; |
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44 | |
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45 | dst = pipi_new(w, h); |
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46 | dstp = pipi_get_pixels(dst, PIPI_PIXELS_RGBA_F32); |
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47 | dstdata = (float *)dstp->pixels; |
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48 | |
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49 | sw = src->w; sh = src->h; |
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50 | dw = dst->w; dh = dst->h; |
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51 | invswsh = 1.0f / (sw * sh); |
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52 | |
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53 | aline = malloc(4 * dw * sizeof(float)); |
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54 | line = malloc(4 * dw * sizeof(float)); |
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55 | |
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56 | memset(line, 0, 4 * dw * sizeof(float)); |
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57 | remy = 0; |
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58 | |
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59 | for(y = 0, y0 = 0; y < dh; y++) |
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60 | { |
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61 | int toty = 0, ny; |
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62 | |
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63 | memset(aline, 0, 4 * dw * sizeof(float)); |
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64 | |
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65 | while(toty < sh) |
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66 | { |
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67 | if(remy == 0) |
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68 | { |
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69 | float r = 0, g = 0, b = 0, a = 0; |
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70 | int remx = 0; |
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71 | |
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72 | for(x = 0, x0 = 0; x < dw; x++) |
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73 | { |
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74 | float ar = 0, ag = 0, ab = 0, aa = 0; |
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75 | int totx = 0, nx; |
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76 | |
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77 | while(totx < sw) |
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78 | { |
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79 | if(remx == 0) |
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80 | { |
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81 | r = srcdata[(y0 * sw + x0) * 4]; |
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82 | g = srcdata[(y0 * sw + x0) * 4 + 1]; |
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83 | b = srcdata[(y0 * sw + x0) * 4 + 2]; |
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84 | a = srcdata[(y0 * sw + x0) * 4 + 3]; |
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85 | x0++; |
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86 | remx = dw; |
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87 | } |
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88 | |
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89 | nx = (totx + remx <= sw) ? remx : sw - totx; |
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90 | ar += nx * r; ag += nx * g; ab += nx * b; aa += nx * a; |
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91 | totx += nx; |
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92 | remx -= nx; |
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93 | } |
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94 | |
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95 | line[4 * x] = ar; |
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96 | line[4 * x + 1] = ag; |
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97 | line[4 * x + 2] = ab; |
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98 | line[4 * x + 3] = aa; |
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99 | } |
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100 | |
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101 | y0++; |
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102 | remy = dh; |
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103 | } |
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104 | |
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105 | ny = (toty + remy <= sh) ? remy : sh - toty; |
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106 | for(x = 0; x < dw; x++) |
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107 | { |
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108 | aline[4 * x] += ny * line[4 * x]; |
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109 | aline[4 * x + 1] += ny * line[4 * x + 1]; |
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110 | aline[4 * x + 2] += ny * line[4 * x + 2]; |
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111 | aline[4 * x + 3] += ny * line[4 * x + 3]; |
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112 | } |
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113 | toty += ny; |
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114 | remy -= ny; |
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115 | } |
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116 | |
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117 | for(x = 0; x < dw; x++) |
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118 | { |
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119 | dstdata[(y * dw + x) * 4] = aline[4 * x] * invswsh; |
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120 | dstdata[(y * dw + x) * 4 + 1] = aline[4 * x + 1] * invswsh; |
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121 | dstdata[(y * dw + x) * 4 + 2] = aline[4 * x + 2] * invswsh; |
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122 | dstdata[(y * dw + x) * 4 + 3] = aline[4 * x + 3] * invswsh; |
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123 | } |
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124 | } |
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125 | |
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126 | free(aline); |
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127 | free(line); |
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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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