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/*
* 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);
}
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