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Diffstat (limited to 'libavfilter/edge_common.c')
| -rw-r--r-- | libavfilter/edge_common.c | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/libavfilter/edge_common.c b/libavfilter/edge_common.c new file mode 100644 index 0000000000..d72e8521cd --- /dev/null +++ b/libavfilter/edge_common.c @@ -0,0 +1,181 @@ +/* + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * FFmpeg is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#include "edge_common.h" + +// Internal helper for ff_sobel() +static int get_rounded_direction(int gx, int gy) +{ + /* reference angles: + * tan( pi/8) = sqrt(2)-1 + * tan(3pi/8) = sqrt(2)+1 + * Gy/Gx is the tangent of the angle (theta), so Gy/Gx is compared against + * <ref-angle>, or more simply Gy against <ref-angle>*Gx + * + * Gx and Gy bounds = [-1020;1020], using 16-bit arithmetic: + * round((sqrt(2)-1) * (1<<16)) = 27146 + * round((sqrt(2)+1) * (1<<16)) = 158218 + */ + if (gx) { + int tanpi8gx, tan3pi8gx; + + if (gx < 0) + gx = -gx, gy = -gy; + gy *= (1 << 16); + tanpi8gx = 27146 * gx; + tan3pi8gx = 158218 * gx; + if (gy > -tan3pi8gx && gy < -tanpi8gx) return DIRECTION_45UP; + if (gy > -tanpi8gx && gy < tanpi8gx) return DIRECTION_HORIZONTAL; + if (gy > tanpi8gx && gy < tan3pi8gx) return DIRECTION_45DOWN; + } + return DIRECTION_VERTICAL; +} + +// Simple sobel operator to get rounded gradients +void 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) +{ + int i, j; + + for (j = 1; j < h - 1; j++) { + dst += dst_linesize; + dir += dir_linesize; + src += src_linesize; + for (i = 1; i < w - 1; i++) { + const int gx = + -1*src[-src_linesize + i-1] + 1*src[-src_linesize + i+1] + -2*src[ i-1] + 2*src[ i+1] + -1*src[ src_linesize + i-1] + 1*src[ src_linesize + i+1]; + const int gy = + -1*src[-src_linesize + i-1] + 1*src[ src_linesize + i-1] + -2*src[-src_linesize + i ] + 2*src[ src_linesize + i ] + -1*src[-src_linesize + i+1] + 1*src[ src_linesize + i+1]; + + dst[i] = FFABS(gx) + FFABS(gy); + dir[i] = get_rounded_direction(gx, gy); + } + } +} + +// Filters rounded gradients to drop all non-maxima +// Expects gradients generated by ff_sobel() +// Expects zero's destination buffer +void 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) +{ + int i, j; + +#define COPY_MAXIMA(ay, ax, by, bx) do { \ + if (src[i] > src[(ay)*src_linesize + i+(ax)] && \ + src[i] > src[(by)*src_linesize + i+(bx)]) \ + dst[i] = av_clip_uint8(src[i]); \ +} while (0) + + for (j = 1; j < h - 1; j++) { + dst += dst_linesize; + dir += dir_linesize; + src += src_linesize; + for (i = 1; i < w - 1; i++) { + switch (dir[i]) { + case DIRECTION_45UP: COPY_MAXIMA( 1, -1, -1, 1); break; + case DIRECTION_45DOWN: COPY_MAXIMA(-1, -1, 1, 1); break; + case DIRECTION_HORIZONTAL: COPY_MAXIMA( 0, -1, 0, 1); break; + case DIRECTION_VERTICAL: COPY_MAXIMA(-1, 0, 1, 0); break; + } + } + } +} + +// Filter to keep all pixels > high, and keep all pixels > low where all surrounding pixels > high +void ff_double_threshold(int low, int high, int w, int h, + uint8_t *dst, int dst_linesize, + const uint8_t *src, int src_linesize) +{ + int i, j; + + for (j = 0; j < h; j++) { + for (i = 0; i < w; i++) { + if (src[i] > high) { + dst[i] = src[i]; + continue; + } + + if (!(!i || i == w - 1 || !j || j == h - 1) && + src[i] > low && + (src[-src_linesize + i-1] > high || + src[-src_linesize + i ] > high || + src[-src_linesize + i+1] > high || + src[ i-1] > high || + src[ i+1] > high || + src[ src_linesize + i-1] > high || + src[ src_linesize + i ] > high || + src[ src_linesize + i+1] > high)) + dst[i] = src[i]; + else + dst[i] = 0; + } + dst += dst_linesize; + src += src_linesize; + } +} + +// Applies gaussian blur, using 5x5 kernels, sigma = 1.4 +void ff_gaussian_blur(int w, int h, + uint8_t *dst, int dst_linesize, + const uint8_t *src, int src_linesize) +{ + int i, j; + + memcpy(dst, src, w); dst += dst_linesize; src += src_linesize; + memcpy(dst, src, w); dst += dst_linesize; src += src_linesize; + for (j = 2; j < h - 2; j++) { + dst[0] = src[0]; + dst[1] = src[1]; + for (i = 2; i < w - 2; i++) { + /* Gaussian mask of size 5x5 with sigma = 1.4 */ + dst[i] = ((src[-2*src_linesize + i-2] + src[2*src_linesize + i-2]) * 2 + + (src[-2*src_linesize + i-1] + src[2*src_linesize + i-1]) * 4 + + (src[-2*src_linesize + i ] + src[2*src_linesize + i ]) * 5 + + (src[-2*src_linesize + i+1] + src[2*src_linesize + i+1]) * 4 + + (src[-2*src_linesize + i+2] + src[2*src_linesize + i+2]) * 2 + + + (src[ -src_linesize + i-2] + src[ src_linesize + i-2]) * 4 + + (src[ -src_linesize + i-1] + src[ src_linesize + i-1]) * 9 + + (src[ -src_linesize + i ] + src[ src_linesize + i ]) * 12 + + (src[ -src_linesize + i+1] + src[ src_linesize + i+1]) * 9 + + (src[ -src_linesize + i+2] + src[ src_linesize + i+2]) * 4 + + + src[i-2] * 5 + + src[i-1] * 12 + + src[i ] * 15 + + src[i+1] * 12 + + src[i+2] * 5) / 159; + } + dst[i ] = src[i ]; + dst[i + 1] = src[i + 1]; + + dst += dst_linesize; + src += src_linesize; + } + memcpy(dst, src, w); dst += dst_linesize; src += src_linesize; + memcpy(dst, src, w); +} |