1 /*
2 * This file is part of FFmpeg.
3 *
4 * FFmpeg is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2.1 of the License, or (at your option) any later version.
8 *
9 * FFmpeg is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Lesser General Public License for more details.
13 *
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with FFmpeg; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17 */
18
19 #include "edge_common.h"
20
21 // Internal helper for ff_sobel()
get_rounded_direction(int gx,int gy)22 static int get_rounded_direction(int gx, int gy)
23 {
24 /* reference angles:
25 * tan( pi/8) = sqrt(2)-1
26 * tan(3pi/8) = sqrt(2)+1
27 * Gy/Gx is the tangent of the angle (theta), so Gy/Gx is compared against
28 * <ref-angle>, or more simply Gy against <ref-angle>*Gx
29 *
30 * Gx and Gy bounds = [-1020;1020], using 16-bit arithmetic:
31 * round((sqrt(2)-1) * (1<<16)) = 27146
32 * round((sqrt(2)+1) * (1<<16)) = 158218
33 */
34 if (gx) {
35 int tanpi8gx, tan3pi8gx;
36
37 if (gx < 0)
38 gx = -gx, gy = -gy;
39 gy *= (1 << 16);
40 tanpi8gx = 27146 * gx;
41 tan3pi8gx = 158218 * gx;
42 if (gy > -tan3pi8gx && gy < -tanpi8gx) return DIRECTION_45UP;
43 if (gy > -tanpi8gx && gy < tanpi8gx) return DIRECTION_HORIZONTAL;
44 if (gy > tanpi8gx && gy < tan3pi8gx) return DIRECTION_45DOWN;
45 }
46 return DIRECTION_VERTICAL;
47 }
48
49 // Simple sobel operator to get rounded gradients
ff_sobel(int w,int h,uint16_t * dst,int dst_linesize,int8_t * dir,int dir_linesize,const uint8_t * src,int src_linesize)50 void ff_sobel(int w, int h,
51 uint16_t *dst, int dst_linesize,
52 int8_t *dir, int dir_linesize,
53 const uint8_t *src, int src_linesize)
54 {
55 int i, j;
56
57 for (j = 1; j < h - 1; j++) {
58 dst += dst_linesize;
59 dir += dir_linesize;
60 src += src_linesize;
61 for (i = 1; i < w - 1; i++) {
62 const int gx =
63 -1*src[-src_linesize + i-1] + 1*src[-src_linesize + i+1]
64 -2*src[ i-1] + 2*src[ i+1]
65 -1*src[ src_linesize + i-1] + 1*src[ src_linesize + i+1];
66 const int gy =
67 -1*src[-src_linesize + i-1] + 1*src[ src_linesize + i-1]
68 -2*src[-src_linesize + i ] + 2*src[ src_linesize + i ]
69 -1*src[-src_linesize + i+1] + 1*src[ src_linesize + i+1];
70
71 dst[i] = FFABS(gx) + FFABS(gy);
72 dir[i] = get_rounded_direction(gx, gy);
73 }
74 }
75 }
76
77 // Filters rounded gradients to drop all non-maxima
78 // Expects gradients generated by ff_sobel()
79 // Expects zero's destination buffer
ff_non_maximum_suppression(int w,int h,uint8_t * dst,int dst_linesize,const int8_t * dir,int dir_linesize,const uint16_t * src,int src_linesize)80 void ff_non_maximum_suppression(int w, int h,
81 uint8_t *dst, int dst_linesize,
82 const int8_t *dir, int dir_linesize,
83 const uint16_t *src, int src_linesize)
84 {
85 int i, j;
86
87 #define COPY_MAXIMA(ay, ax, by, bx) do { \
88 if (src[i] > src[(ay)*src_linesize + i+(ax)] && \
89 src[i] > src[(by)*src_linesize + i+(bx)]) \
90 dst[i] = av_clip_uint8(src[i]); \
91 } while (0)
92
93 for (j = 1; j < h - 1; j++) {
94 dst += dst_linesize;
95 dir += dir_linesize;
96 src += src_linesize;
97 for (i = 1; i < w - 1; i++) {
98 switch (dir[i]) {
99 case DIRECTION_45UP: COPY_MAXIMA( 1, -1, -1, 1); break;
100 case DIRECTION_45DOWN: COPY_MAXIMA(-1, -1, 1, 1); break;
101 case DIRECTION_HORIZONTAL: COPY_MAXIMA( 0, -1, 0, 1); break;
102 case DIRECTION_VERTICAL: COPY_MAXIMA(-1, 0, 1, 0); break;
103 }
104 }
105 }
106 }
107
108 // Filter to keep all pixels > high, and keep all pixels > low where all surrounding pixels > high
ff_double_threshold(int low,int high,int w,int h,uint8_t * dst,int dst_linesize,const uint8_t * src,int src_linesize)109 void ff_double_threshold(int low, int high, int w, int h,
110 uint8_t *dst, int dst_linesize,
111 const uint8_t *src, int src_linesize)
112 {
113 int i, j;
114
115 for (j = 0; j < h; j++) {
116 for (i = 0; i < w; i++) {
117 if (src[i] > high) {
118 dst[i] = src[i];
119 continue;
120 }
121
122 if (!(!i || i == w - 1 || !j || j == h - 1) &&
123 src[i] > low &&
124 (src[-src_linesize + i-1] > high ||
125 src[-src_linesize + i ] > high ||
126 src[-src_linesize + i+1] > high ||
127 src[ i-1] > high ||
128 src[ i+1] > high ||
129 src[ src_linesize + i-1] > high ||
130 src[ src_linesize + i ] > high ||
131 src[ src_linesize + i+1] > high))
132 dst[i] = src[i];
133 else
134 dst[i] = 0;
135 }
136 dst += dst_linesize;
137 src += src_linesize;
138 }
139 }
140
141 // Applies gaussian blur, using 5x5 kernels, sigma = 1.4
ff_gaussian_blur(int w,int h,uint8_t * dst,int dst_linesize,const uint8_t * src,int src_linesize)142 void ff_gaussian_blur(int w, int h,
143 uint8_t *dst, int dst_linesize,
144 const uint8_t *src, int src_linesize)
145 {
146 int i, j;
147
148 memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
149 memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
150 for (j = 2; j < h - 2; j++) {
151 dst[0] = src[0];
152 dst[1] = src[1];
153 for (i = 2; i < w - 2; i++) {
154 /* Gaussian mask of size 5x5 with sigma = 1.4 */
155 dst[i] = ((src[-2*src_linesize + i-2] + src[2*src_linesize + i-2]) * 2
156 + (src[-2*src_linesize + i-1] + src[2*src_linesize + i-1]) * 4
157 + (src[-2*src_linesize + i ] + src[2*src_linesize + i ]) * 5
158 + (src[-2*src_linesize + i+1] + src[2*src_linesize + i+1]) * 4
159 + (src[-2*src_linesize + i+2] + src[2*src_linesize + i+2]) * 2
160
161 + (src[ -src_linesize + i-2] + src[ src_linesize + i-2]) * 4
162 + (src[ -src_linesize + i-1] + src[ src_linesize + i-1]) * 9
163 + (src[ -src_linesize + i ] + src[ src_linesize + i ]) * 12
164 + (src[ -src_linesize + i+1] + src[ src_linesize + i+1]) * 9
165 + (src[ -src_linesize + i+2] + src[ src_linesize + i+2]) * 4
166
167 + src[i-2] * 5
168 + src[i-1] * 12
169 + src[i ] * 15
170 + src[i+1] * 12
171 + src[i+2] * 5) / 159;
172 }
173 dst[i ] = src[i ];
174 dst[i + 1] = src[i + 1];
175
176 dst += dst_linesize;
177 src += src_linesize;
178 }
179 memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
180 memcpy(dst, src, w);
181 }
182