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/*
Copyright 2007 Niels Martin Hansen
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
Contact:
E-mail: <jiifurusu@gmail.com>
IRC: jfs in #aegisub on irc.rizon.net
*/
#pragma once
#ifdef _OPENMP
#include <omp.h>
#endif
#include <math.h>
// Filter an image in horizontal direction with a one-dimensional filter
// PixelWidth is the distance in bytes between pixels
template<ptrdiff_t PixelDist>
void SeparableFilterX(unsigned char *src, unsigned char *dst, int width, int height, ptrdiff_t stride, int *kernel, int kernel_size, int divisor)
{
#pragma omp parallel for
for (int y = 0; y < height; y++) {
unsigned char *in = src + y*stride;
unsigned char *out = dst + y*stride;
for (int x = 0; x < width; x++) {
int accum = 0;
for (int k = 0; k < kernel_size; k++) {
int xofs = k - kernel_size/2;
if (x+xofs < 0) xofs += width;
if (x+xofs >= width) xofs -= width;
accum += (int)(in[xofs*PixelDist] * kernel[k]);
}
accum /= divisor;
if (accum > 255) accum = 255;
if (accum < 0) accum = 0;
*out = (unsigned char)accum;
in+=PixelDist;
out+=PixelDist;
}
}
}
// Filter an image in vertical direction with a one-dimensional filter
// This one templated with PixelWidth since the channel interlacing is horizontal only,
// filtering once vertically will automatically catch all channels.
// (Width must be multiplied by pixel width for that to happen though.)
template<ptrdiff_t PixelDist>
void SeparableFilterY(unsigned char *src, unsigned char *dst, int width, int height, ptrdiff_t stride, int *kernel, int kernel_size, int divisor)
{
width *= PixelDist;
#pragma omp parallel for
for (int x = 0; x < width; x+=PixelDist) {
unsigned char *in = src + x;
unsigned char *out = dst + x;
for (int y = 0; y < height; y++) {
int accum = 0;
for (int k = 0; k < kernel_size; k++) {
int yofs = k - kernel_size/2;
if (y+yofs < 0) yofs += height;
if (y+yofs >= height) yofs -= height;
accum += (int)(in[yofs*stride] * kernel[k]);
}
accum /= divisor;
if (accum > 255) accum = 255;
if (accum < 0) accum = 0;
*out = (unsigned char)accum;
in += stride;
out += stride;
}
}
}
static inline double NormalDist(double sigma, double x)
{
if (sigma <= 0 && x == 0) return 1;
else if (sigma <= 0) return 0;
else return exp(-(x*x)/(2*sigma*sigma)) / (sigma * sqrt(2*3.1415926535));
}
struct GaussianKernel {
int *kernel;
int width;
int divisor;
inline GaussianKernel(double sigma)
{
width = (int)(sigma*3 + 0.5) | 1; // binary-or with 1 to make sure the number is odd
if (width < 3) width = 3;
kernel = DNew int[width];
kernel[width/2] = (int)(NormalDist(sigma, 0) * 255);
divisor = kernel[width/2];
for (int x = width/2-1; x >= 0; x--) {
int val = (int)(NormalDist(sigma, width/2-x) * 255 + 0.5);
divisor += val*2;
kernel[x] = val;
kernel[width - x - 1] = val;
}
}
inline ~GaussianKernel()
{
delete[] kernel;
}
};
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