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https://github.com/FFmpeg/FFmpeg.git
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120 lines
4.1 KiB
C
120 lines
4.1 KiB
C
/*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "edge_common.h"
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// Internal helper for ff_sobel()
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static int get_rounded_direction(int gx, int gy)
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{
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/* reference angles:
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* tan( pi/8) = sqrt(2)-1
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* tan(3pi/8) = sqrt(2)+1
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* Gy/Gx is the tangent of the angle (theta), so Gy/Gx is compared against
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* <ref-angle>, or more simply Gy against <ref-angle>*Gx
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*
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* Gx and Gy bounds = [-1020;1020], using 16-bit arithmetic:
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* round((sqrt(2)-1) * (1<<16)) = 27146
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* round((sqrt(2)+1) * (1<<16)) = 158218
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*/
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if (gx) {
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int tanpi8gx, tan3pi8gx;
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if (gx < 0)
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gx = -gx, gy = -gy;
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gy *= (1 << 16);
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tanpi8gx = 27146 * gx;
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tan3pi8gx = 158218 * gx;
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if (gy > -tan3pi8gx && gy < -tanpi8gx) return DIRECTION_45UP;
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if (gy > -tanpi8gx && gy < tanpi8gx) return DIRECTION_HORIZONTAL;
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if (gy > tanpi8gx && gy < tan3pi8gx) return DIRECTION_45DOWN;
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}
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return DIRECTION_VERTICAL;
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}
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#undef DEPTH
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#define DEPTH 8
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#include "edge_template.c"
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#undef DEPTH
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#define DEPTH 16
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#include "edge_template.c"
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// Filters rounded gradients to drop all non-maxima
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// Expects gradients generated by ff_sobel()
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// Expects zero's destination buffer
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void ff_non_maximum_suppression(int w, int h,
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uint8_t *dst, int dst_linesize,
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const int8_t *dir, int dir_linesize,
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const uint16_t *src, int src_linesize)
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{
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int i, j;
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#define COPY_MAXIMA(ay, ax, by, bx) do { \
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if (src[i] > src[(ay)*src_linesize + i+(ax)] && \
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src[i] > src[(by)*src_linesize + i+(bx)]) \
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dst[i] = av_clip_uint8(src[i]); \
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} while (0)
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for (j = 1; j < h - 1; j++) {
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dst += dst_linesize;
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dir += dir_linesize;
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src += src_linesize;
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for (i = 1; i < w - 1; i++) {
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switch (dir[i]) {
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case DIRECTION_45UP: COPY_MAXIMA( 1, -1, -1, 1); break;
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case DIRECTION_45DOWN: COPY_MAXIMA(-1, -1, 1, 1); break;
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case DIRECTION_HORIZONTAL: COPY_MAXIMA( 0, -1, 0, 1); break;
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case DIRECTION_VERTICAL: COPY_MAXIMA(-1, 0, 1, 0); break;
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}
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}
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}
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}
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// Filter to keep all pixels > high, and keep all pixels > low where all surrounding pixels > high
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void ff_double_threshold(int low, int high, int w, int h,
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uint8_t *dst, int dst_linesize,
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const uint8_t *src, int src_linesize)
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{
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int i, j;
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for (j = 0; j < h; j++) {
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for (i = 0; i < w; i++) {
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if (src[i] > high) {
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dst[i] = src[i];
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continue;
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}
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if (!(!i || i == w - 1 || !j || j == h - 1) &&
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src[i] > low &&
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(src[-src_linesize + i-1] > high ||
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src[-src_linesize + i ] > high ||
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src[-src_linesize + i+1] > high ||
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src[ i-1] > high ||
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src[ i+1] > high ||
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src[ src_linesize + i-1] > high ||
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src[ src_linesize + i ] > high ||
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src[ src_linesize + i+1] > high))
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dst[i] = src[i];
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else
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dst[i] = 0;
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}
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dst += dst_linesize;
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src += src_linesize;
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}
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}
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