/* * 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;} #undef DEPTH#define DEPTH 8#include "edge_template.c" #undef DEPTH#define DEPTH 16#include "edge_template.c" // Filters rounded gradients to drop all non-maxima// Expects gradients generated by ff_sobel()// Expects zero's destination buffervoid 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 > highvoid 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;    }}