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path: root/libavfilter/vf_edgedetect.c (plain)
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1/*
2 * Copyright (c) 2012-2014 Clément Bœsch <u pkh me>
3 *
4 * This file is part of FFmpeg.
5 *
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21/**
22 * @file
23 * Edge detection filter
24 *
25 * @see https://en.wikipedia.org/wiki/Canny_edge_detector
26 */
27
28#include "libavutil/avassert.h"
29#include "libavutil/opt.h"
30#include "avfilter.h"
31#include "formats.h"
32#include "internal.h"
33#include "video.h"
34
35enum FilterMode {
36 MODE_WIRES,
37 MODE_COLORMIX,
38 NB_MODE
39};
40
41struct plane_info {
42 uint8_t *tmpbuf;
43 uint16_t *gradients;
44 char *directions;
45};
46
47typedef struct {
48 const AVClass *class;
49 struct plane_info planes[3];
50 int nb_planes;
51 double low, high;
52 uint8_t low_u8, high_u8;
53 int mode;
54} EdgeDetectContext;
55
56#define OFFSET(x) offsetof(EdgeDetectContext, x)
57#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
58static const AVOption edgedetect_options[] = {
59 { "high", "set high threshold", OFFSET(high), AV_OPT_TYPE_DOUBLE, {.dbl=50/255.}, 0, 1, FLAGS },
60 { "low", "set low threshold", OFFSET(low), AV_OPT_TYPE_DOUBLE, {.dbl=20/255.}, 0, 1, FLAGS },
61 { "mode", "set mode", OFFSET(mode), AV_OPT_TYPE_INT, {.i64=MODE_WIRES}, 0, NB_MODE-1, FLAGS, "mode" },
62 { "wires", "white/gray wires on black", 0, AV_OPT_TYPE_CONST, {.i64=MODE_WIRES}, INT_MIN, INT_MAX, FLAGS, "mode" },
63 { "colormix", "mix colors", 0, AV_OPT_TYPE_CONST, {.i64=MODE_COLORMIX}, INT_MIN, INT_MAX, FLAGS, "mode" },
64 { NULL }
65};
66
67AVFILTER_DEFINE_CLASS(edgedetect);
68
69static av_cold int init(AVFilterContext *ctx)
70{
71 EdgeDetectContext *edgedetect = ctx->priv;
72
73 edgedetect->low_u8 = edgedetect->low * 255. + .5;
74 edgedetect->high_u8 = edgedetect->high * 255. + .5;
75 return 0;
76}
77
78static int query_formats(AVFilterContext *ctx)
79{
80 const EdgeDetectContext *edgedetect = ctx->priv;
81 static const enum AVPixelFormat wires_pix_fmts[] = {AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE};
82 static const enum AVPixelFormat colormix_pix_fmts[] = {AV_PIX_FMT_GBRP, AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE};
83 AVFilterFormats *fmts_list;
84 const enum AVPixelFormat *pix_fmts = NULL;
85
86 if (edgedetect->mode == MODE_WIRES) {
87 pix_fmts = wires_pix_fmts;
88 } else if (edgedetect->mode == MODE_COLORMIX) {
89 pix_fmts = colormix_pix_fmts;
90 } else {
91 av_assert0(0);
92 }
93 fmts_list = ff_make_format_list(pix_fmts);
94 if (!fmts_list)
95 return AVERROR(ENOMEM);
96 return ff_set_common_formats(ctx, fmts_list);
97}
98
99static int config_props(AVFilterLink *inlink)
100{
101 int p;
102 AVFilterContext *ctx = inlink->dst;
103 EdgeDetectContext *edgedetect = ctx->priv;
104
105 edgedetect->nb_planes = inlink->format == AV_PIX_FMT_GRAY8 ? 1 : 3;
106 for (p = 0; p < edgedetect->nb_planes; p++) {
107 struct plane_info *plane = &edgedetect->planes[p];
108
109 plane->tmpbuf = av_malloc(inlink->w * inlink->h);
110 plane->gradients = av_calloc(inlink->w * inlink->h, sizeof(*plane->gradients));
111 plane->directions = av_malloc(inlink->w * inlink->h);
112 if (!plane->tmpbuf || !plane->gradients || !plane->directions)
113 return AVERROR(ENOMEM);
114 }
115 return 0;
116}
117
118static void gaussian_blur(AVFilterContext *ctx, int w, int h,
119 uint8_t *dst, int dst_linesize,
120 const uint8_t *src, int src_linesize)
121{
122 int i, j;
123
124 memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
125 memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
126 for (j = 2; j < h - 2; j++) {
127 dst[0] = src[0];
128 dst[1] = src[1];
129 for (i = 2; i < w - 2; i++) {
130 /* Gaussian mask of size 5x5 with sigma = 1.4 */
131 dst[i] = ((src[-2*src_linesize + i-2] + src[2*src_linesize + i-2]) * 2
132 + (src[-2*src_linesize + i-1] + src[2*src_linesize + i-1]) * 4
133 + (src[-2*src_linesize + i ] + src[2*src_linesize + i ]) * 5
134 + (src[-2*src_linesize + i+1] + src[2*src_linesize + i+1]) * 4
135 + (src[-2*src_linesize + i+2] + src[2*src_linesize + i+2]) * 2
136
137 + (src[ -src_linesize + i-2] + src[ src_linesize + i-2]) * 4
138 + (src[ -src_linesize + i-1] + src[ src_linesize + i-1]) * 9
139 + (src[ -src_linesize + i ] + src[ src_linesize + i ]) * 12
140 + (src[ -src_linesize + i+1] + src[ src_linesize + i+1]) * 9
141 + (src[ -src_linesize + i+2] + src[ src_linesize + i+2]) * 4
142
143 + src[i-2] * 5
144 + src[i-1] * 12
145 + src[i ] * 15
146 + src[i+1] * 12
147 + src[i+2] * 5) / 159;
148 }
149 dst[i ] = src[i ];
150 dst[i + 1] = src[i + 1];
151
152 dst += dst_linesize;
153 src += src_linesize;
154 }
155 memcpy(dst, src, w); dst += dst_linesize; src += src_linesize;
156 memcpy(dst, src, w);
157}
158
159enum {
160 DIRECTION_45UP,
161 DIRECTION_45DOWN,
162 DIRECTION_HORIZONTAL,
163 DIRECTION_VERTICAL,
164};
165
166static int get_rounded_direction(int gx, int gy)
167{
168 /* reference angles:
169 * tan( pi/8) = sqrt(2)-1
170 * tan(3pi/8) = sqrt(2)+1
171 * Gy/Gx is the tangent of the angle (theta), so Gy/Gx is compared against
172 * <ref-angle>, or more simply Gy against <ref-angle>*Gx
173 *
174 * Gx and Gy bounds = [-1020;1020], using 16-bit arithmetic:
175 * round((sqrt(2)-1) * (1<<16)) = 27146
176 * round((sqrt(2)+1) * (1<<16)) = 158218
177 */
178 if (gx) {
179 int tanpi8gx, tan3pi8gx;
180
181 if (gx < 0)
182 gx = -gx, gy = -gy;
183 gy <<= 16;
184 tanpi8gx = 27146 * gx;
185 tan3pi8gx = 158218 * gx;
186 if (gy > -tan3pi8gx && gy < -tanpi8gx) return DIRECTION_45UP;
187 if (gy > -tanpi8gx && gy < tanpi8gx) return DIRECTION_HORIZONTAL;
188 if (gy > tanpi8gx && gy < tan3pi8gx) return DIRECTION_45DOWN;
189 }
190 return DIRECTION_VERTICAL;
191}
192
193static void sobel(int w, int h,
194 uint16_t *dst, int dst_linesize,
195 int8_t *dir, int dir_linesize,
196 const uint8_t *src, int src_linesize)
197{
198 int i, j;
199
200 for (j = 1; j < h - 1; j++) {
201 dst += dst_linesize;
202 dir += dir_linesize;
203 src += src_linesize;
204 for (i = 1; i < w - 1; i++) {
205 const int gx =
206 -1*src[-src_linesize + i-1] + 1*src[-src_linesize + i+1]
207 -2*src[ i-1] + 2*src[ i+1]
208 -1*src[ src_linesize + i-1] + 1*src[ src_linesize + i+1];
209 const int gy =
210 -1*src[-src_linesize + i-1] + 1*src[ src_linesize + i-1]
211 -2*src[-src_linesize + i ] + 2*src[ src_linesize + i ]
212 -1*src[-src_linesize + i+1] + 1*src[ src_linesize + i+1];
213
214 dst[i] = FFABS(gx) + FFABS(gy);
215 dir[i] = get_rounded_direction(gx, gy);
216 }
217 }
218}
219
220static void non_maximum_suppression(int w, int h,
221 uint8_t *dst, int dst_linesize,
222 const int8_t *dir, int dir_linesize,
223 const uint16_t *src, int src_linesize)
224{
225 int i, j;
226
227#define COPY_MAXIMA(ay, ax, by, bx) do { \
228 if (src[i] > src[(ay)*src_linesize + i+(ax)] && \
229 src[i] > src[(by)*src_linesize + i+(bx)]) \
230 dst[i] = av_clip_uint8(src[i]); \
231} while (0)
232
233 for (j = 1; j < h - 1; j++) {
234 dst += dst_linesize;
235 dir += dir_linesize;
236 src += src_linesize;
237 for (i = 1; i < w - 1; i++) {
238 switch (dir[i]) {
239 case DIRECTION_45UP: COPY_MAXIMA( 1, -1, -1, 1); break;
240 case DIRECTION_45DOWN: COPY_MAXIMA(-1, -1, 1, 1); break;
241 case DIRECTION_HORIZONTAL: COPY_MAXIMA( 0, -1, 0, 1); break;
242 case DIRECTION_VERTICAL: COPY_MAXIMA(-1, 0, 1, 0); break;
243 }
244 }
245 }
246}
247
248static void double_threshold(int low, int high, int w, int h,
249 uint8_t *dst, int dst_linesize,
250 const uint8_t *src, int src_linesize)
251{
252 int i, j;
253
254 for (j = 0; j < h; j++) {
255 for (i = 0; i < w; i++) {
256 if (src[i] > high) {
257 dst[i] = src[i];
258 continue;
259 }
260
261 if ((!i || i == w - 1 || !j || j == h - 1) &&
262 src[i] > low &&
263 (src[-src_linesize + i-1] > high ||
264 src[-src_linesize + i ] > high ||
265 src[-src_linesize + i+1] > high ||
266 src[ i-1] > high ||
267 src[ i+1] > high ||
268 src[ src_linesize + i-1] > high ||
269 src[ src_linesize + i ] > high ||
270 src[ src_linesize + i+1] > high))
271 dst[i] = src[i];
272 else
273 dst[i] = 0;
274 }
275 dst += dst_linesize;
276 src += src_linesize;
277 }
278}
279
280static void color_mix(int w, int h,
281 uint8_t *dst, int dst_linesize,
282 const uint8_t *src, int src_linesize)
283{
284 int i, j;
285
286 for (j = 0; j < h; j++) {
287 for (i = 0; i < w; i++)
288 dst[i] = (dst[i] + src[i]) >> 1;
289 dst += dst_linesize;
290 src += src_linesize;
291 }
292}
293
294static int filter_frame(AVFilterLink *inlink, AVFrame *in)
295{
296 AVFilterContext *ctx = inlink->dst;
297 EdgeDetectContext *edgedetect = ctx->priv;
298 AVFilterLink *outlink = ctx->outputs[0];
299 int p, direct = 0;
300 AVFrame *out;
301
302 if (edgedetect->mode != MODE_COLORMIX && av_frame_is_writable(in)) {
303 direct = 1;
304 out = in;
305 } else {
306 out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
307 if (!out) {
308 av_frame_free(&in);
309 return AVERROR(ENOMEM);
310 }
311 av_frame_copy_props(out, in);
312 }
313
314 for (p = 0; p < edgedetect->nb_planes; p++) {
315 struct plane_info *plane = &edgedetect->planes[p];
316 uint8_t *tmpbuf = plane->tmpbuf;
317 uint16_t *gradients = plane->gradients;
318 int8_t *directions = plane->directions;
319
320 /* gaussian filter to reduce noise */
321 gaussian_blur(ctx, inlink->w, inlink->h,
322 tmpbuf, inlink->w,
323 in->data[p], in->linesize[p]);
324
325 /* compute the 16-bits gradients and directions for the next step */
326 sobel(inlink->w, inlink->h,
327 gradients, inlink->w,
328 directions,inlink->w,
329 tmpbuf, inlink->w);
330
331 /* non_maximum_suppression() will actually keep & clip what's necessary and
332 * ignore the rest, so we need a clean output buffer */
333 memset(tmpbuf, 0, inlink->w * inlink->h);
334 non_maximum_suppression(inlink->w, inlink->h,
335 tmpbuf, inlink->w,
336 directions,inlink->w,
337 gradients, inlink->w);
338
339 /* keep high values, or low values surrounded by high values */
340 double_threshold(edgedetect->low_u8, edgedetect->high_u8,
341 inlink->w, inlink->h,
342 out->data[p], out->linesize[p],
343 tmpbuf, inlink->w);
344
345 if (edgedetect->mode == MODE_COLORMIX) {
346 color_mix(inlink->w, inlink->h,
347 out->data[p], out->linesize[p],
348 in->data[p], in->linesize[p]);
349 }
350 }
351
352 if (!direct)
353 av_frame_free(&in);
354 return ff_filter_frame(outlink, out);
355}
356
357static av_cold void uninit(AVFilterContext *ctx)
358{
359 int p;
360 EdgeDetectContext *edgedetect = ctx->priv;
361
362 for (p = 0; p < edgedetect->nb_planes; p++) {
363 struct plane_info *plane = &edgedetect->planes[p];
364 av_freep(&plane->tmpbuf);
365 av_freep(&plane->gradients);
366 av_freep(&plane->directions);
367 }
368}
369
370static const AVFilterPad edgedetect_inputs[] = {
371 {
372 .name = "default",
373 .type = AVMEDIA_TYPE_VIDEO,
374 .config_props = config_props,
375 .filter_frame = filter_frame,
376 },
377 { NULL }
378};
379
380static const AVFilterPad edgedetect_outputs[] = {
381 {
382 .name = "default",
383 .type = AVMEDIA_TYPE_VIDEO,
384 },
385 { NULL }
386};
387
388AVFilter ff_vf_edgedetect = {
389 .name = "edgedetect",
390 .description = NULL_IF_CONFIG_SMALL("Detect and draw edge."),
391 .priv_size = sizeof(EdgeDetectContext),
392 .init = init,
393 .uninit = uninit,
394 .query_formats = query_formats,
395 .inputs = edgedetect_inputs,
396 .outputs = edgedetect_outputs,
397 .priv_class = &edgedetect_class,
398 .flags = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
399};
400
generated by cgit at 2024-05-17 01:48:45 (GMT)