1 | /* |
---|
2 | * libpipi Pathetic image processing interface library |
---|
3 | * Copyright (c) 2004-2008 Sam Hocevar <sam@zoy.org> |
---|
4 | * All Rights Reserved |
---|
5 | * |
---|
6 | * $Id$ |
---|
7 | * |
---|
8 | * This library is free software. It comes without any warranty, to |
---|
9 | * the extent permitted by applicable law. You can redistribute it |
---|
10 | * and/or modify it under the terms of the Do What The Fuck You Want |
---|
11 | * To Public License, Version 2, as published by Sam Hocevar. See |
---|
12 | * http://sam.zoy.org/wtfpl/COPYING for more details. |
---|
13 | */ |
---|
14 | |
---|
15 | /* |
---|
16 | * dbs.c: Direct Binary Search dithering functions |
---|
17 | */ |
---|
18 | |
---|
19 | #include "config.h" |
---|
20 | #include "common.h" |
---|
21 | |
---|
22 | #include <string.h> |
---|
23 | #include <stdlib.h> |
---|
24 | |
---|
25 | #include <math.h> |
---|
26 | |
---|
27 | #include "pipi.h" |
---|
28 | #include "pipi_internals.h" |
---|
29 | |
---|
30 | #define CELL 16 |
---|
31 | |
---|
32 | #define N 7 |
---|
33 | #define NN ((N * 2 + 1)) |
---|
34 | |
---|
35 | /* FIXME: though the algorithm is supposed to stop, we do not have a real, |
---|
36 | * guaranteed stop condition here. */ |
---|
37 | |
---|
38 | pipi_image_t *pipi_dither_dbs(pipi_image_t *img) |
---|
39 | { |
---|
40 | double kernel[NN * NN]; |
---|
41 | double t = 0.; |
---|
42 | pipi_image_t *src, *dst, *tmp1, *tmp2; |
---|
43 | pipi_pixels_t *dstp, *tmp1p, *tmp2p; |
---|
44 | int *changelist; |
---|
45 | float *dstdata, *tmp1data, *tmp2data; |
---|
46 | int i, j, x, y, w, h, cw, ch; |
---|
47 | |
---|
48 | /* Build our human visual system kernel. */ |
---|
49 | for(j = 0; j < NN; j++) |
---|
50 | for(i = 0; i < NN; i++) |
---|
51 | { |
---|
52 | double a = (double)(i - N); |
---|
53 | double b = (double)(j - N); |
---|
54 | kernel[j * NN + i] = |
---|
55 | exp(-(a * a + b * b) / (2. * 1.6 * 1.6)) |
---|
56 | + exp(-(a * a + b * b) / (2. * 0.6 * 0.6)); |
---|
57 | t += kernel[j * NN + i]; |
---|
58 | } |
---|
59 | |
---|
60 | for(j = 0; j < NN; j++) |
---|
61 | for(i = 0; i < NN; i++) |
---|
62 | kernel[j * NN + i] /= t; |
---|
63 | |
---|
64 | w = img->w; |
---|
65 | h = img->h; |
---|
66 | |
---|
67 | cw = (w + CELL - 1) / CELL; |
---|
68 | ch = (h + CELL - 1) / CELL; |
---|
69 | changelist = malloc(cw * ch * sizeof(int)); |
---|
70 | memset(changelist, 0, cw * ch * sizeof(int)); |
---|
71 | |
---|
72 | src = pipi_copy(img); |
---|
73 | pipi_getpixels(src, PIPI_PIXELS_Y_F); |
---|
74 | |
---|
75 | tmp1 = pipi_convolution(src, NN, NN, kernel); |
---|
76 | tmp1p = pipi_getpixels(tmp1, PIPI_PIXELS_Y_F); |
---|
77 | tmp1data = (float *)tmp1p->pixels; |
---|
78 | |
---|
79 | dst = pipi_dither_random(src); |
---|
80 | dstp = pipi_getpixels(dst, PIPI_PIXELS_Y_F); |
---|
81 | dstdata = (float *)dstp->pixels; |
---|
82 | |
---|
83 | pipi_free(src); |
---|
84 | |
---|
85 | tmp2 = pipi_convolution(dst, NN, NN, kernel); |
---|
86 | tmp2p = pipi_getpixels(tmp2, PIPI_PIXELS_Y_F); |
---|
87 | tmp2data = (float *)tmp2p->pixels; |
---|
88 | |
---|
89 | for(;;) |
---|
90 | { |
---|
91 | int cx, cy, n; |
---|
92 | int allchanges = 0; |
---|
93 | |
---|
94 | for(cy = 0; cy < ch; cy++) |
---|
95 | for(cx = 0; cx < cw; cx++) |
---|
96 | { |
---|
97 | int changes = 0; |
---|
98 | |
---|
99 | if(changelist[cy * cw + cx] >= 2) |
---|
100 | continue; |
---|
101 | |
---|
102 | for(y = cy * CELL; y < (cy + 1) * CELL; y++) |
---|
103 | for(x = cx * CELL; x < (cx + 1) * CELL; x++) |
---|
104 | { |
---|
105 | double d, d2, e, best = 0.; |
---|
106 | int opx = -1, opy = -1; |
---|
107 | |
---|
108 | d = dstdata[y * w + x]; |
---|
109 | |
---|
110 | /* Compute the effect of a toggle */ |
---|
111 | e = 0.; |
---|
112 | for(j = -N; j < N + 1; j++) |
---|
113 | { |
---|
114 | if(y + j < 0 || y + j >= h) |
---|
115 | continue; |
---|
116 | |
---|
117 | for(i = -N; i < N + 1; i++) |
---|
118 | { |
---|
119 | double m, p, q1, q2; |
---|
120 | |
---|
121 | if(x + i < 0 || x + i >= w) |
---|
122 | continue; |
---|
123 | |
---|
124 | m = kernel[(j + N) * NN + i + N]; |
---|
125 | p = tmp1data[(y + j) * w + x + i]; |
---|
126 | q1 = tmp2data[(y + j) * w + x + i]; |
---|
127 | q2 = q1 - m * d + m * (1. - d); |
---|
128 | e += (q1 - p) * (q1 - p) - (q2 - p) * (q2 - p); |
---|
129 | } |
---|
130 | } |
---|
131 | if(e > best) |
---|
132 | { |
---|
133 | best = e; |
---|
134 | opx = opy = 0; |
---|
135 | } |
---|
136 | |
---|
137 | /* Compute the effect of swaps */ |
---|
138 | for(n = 0; n < 8; n++) |
---|
139 | { |
---|
140 | static int const step[] = |
---|
141 | { 0, 1, 0, -1, -1, 0, 1, 0, -1, -1, -1, 1, 1, -1, 1, 1 }; |
---|
142 | int idx = step[n * 2], idy = step[n * 2 + 1]; |
---|
143 | if(y + idy < 0 || y + idy >= h |
---|
144 | || x + idx < 0 || x + idx >= w) |
---|
145 | continue; |
---|
146 | d2 = dstdata[(y + idy) * w + x + idx]; |
---|
147 | if(d2 == d) |
---|
148 | continue; |
---|
149 | e = 0.; |
---|
150 | for(j = -N; j < N + 1; j++) |
---|
151 | { |
---|
152 | if(y + j < 0 || y + j >= h) |
---|
153 | continue; |
---|
154 | if(j - idy + N < 0 || j - idy + N >= NN) |
---|
155 | continue; |
---|
156 | for(i = -N; i < N + 1; i++) |
---|
157 | { |
---|
158 | double ma, mb, p, q1, q2; |
---|
159 | if(x + i < 0 || x + i >= w) |
---|
160 | continue; |
---|
161 | if(i - idx + N < 0 || i - idx + N >= NN) |
---|
162 | continue; |
---|
163 | ma = kernel[(j + N) * NN + i + N]; |
---|
164 | mb = kernel[(j - idy + N) * NN + i - idx + N]; |
---|
165 | p = tmp1data[(y + j) * w + x + i]; |
---|
166 | q1 = tmp2data[(y + j) * w + x + i]; |
---|
167 | q2 = q1 - ma * d + ma * d2 - mb * d2 + mb * d; |
---|
168 | e += (q1 - p) * (q1 - p) - (q2 - p) * (q2 - p); |
---|
169 | } |
---|
170 | } |
---|
171 | if(e > best) |
---|
172 | { |
---|
173 | best = e; |
---|
174 | opx = idx; |
---|
175 | opy = idy; |
---|
176 | } |
---|
177 | } |
---|
178 | |
---|
179 | /* Apply the change if interesting */ |
---|
180 | if(best <= 0.) |
---|
181 | continue; |
---|
182 | if(opx || opy) |
---|
183 | { |
---|
184 | d2 = dstdata[(y + opy) * w + x + opx]; |
---|
185 | dstdata[(y + opy) * w + x + opx] = d; |
---|
186 | } |
---|
187 | else |
---|
188 | d2 = 1. - d; |
---|
189 | dstdata[y * w + x] = d2; |
---|
190 | for(j = -N; j < N + 1; j++) |
---|
191 | for(i = -N; i < N + 1; i++) |
---|
192 | { |
---|
193 | double m = kernel[(j + N) * NN + i + N]; |
---|
194 | if(y + j >= 0 && y + j < h |
---|
195 | && x + i >= 0 && x + i < w) |
---|
196 | { |
---|
197 | t = tmp2data[(y + j) * w + x + i]; |
---|
198 | tmp2data[(y + j) * w + x + i] = t + m * (d2 - d); |
---|
199 | } |
---|
200 | if((opx || opy) && y + opy + j >= 0 && y + opy + j < h |
---|
201 | && x + opx + i >= 0 && x + opx + i < w) |
---|
202 | { |
---|
203 | t = tmp2data[(y + opy + j) * w + x + opx + i]; |
---|
204 | tmp2data[(y + opy + j) * w + x + opx + i] |
---|
205 | = t + m * (d - d2); |
---|
206 | } |
---|
207 | } |
---|
208 | |
---|
209 | changes++; |
---|
210 | } |
---|
211 | |
---|
212 | if(changes == 0) |
---|
213 | changelist[cy * cw + cx]++; |
---|
214 | |
---|
215 | allchanges += changes; |
---|
216 | } |
---|
217 | |
---|
218 | if(allchanges == 0) |
---|
219 | break; |
---|
220 | } |
---|
221 | |
---|
222 | free(changelist); |
---|
223 | |
---|
224 | pipi_free(tmp1); |
---|
225 | pipi_free(tmp2); |
---|
226 | |
---|
227 | return dst; |
---|
228 | } |
---|
229 | |
---|