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mpv/video/out/dither.c

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/******************************************************************************
dither.c - generate a dithering matrix for downsampling images
Copyright © 2013 Wessel Dankers <wsl@fruit.je>
This file is part of mpv.
mpv 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.
mpv 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 mpv. If not, see <http://www.gnu.org/licenses/>.
You can alternatively redistribute this file 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.
******************************************************************************/
#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <inttypes.h>
#include <string.h>
#include <assert.h>
#include <math.h>
#include <libavutil/lfg.h>
#include "talloc.h"
#include "dither.h"
#define MAX_SIZEB 8
#define MAX_SIZE (1 << MAX_SIZEB)
#define MAX_SIZE2 (MAX_SIZE * MAX_SIZE)
typedef uint_fast32_t index_t;
#define WRAP_SIZE2(k, x) ((index_t)((index_t)(x) & ((k)->size2 - 1)))
#define XY(k, x, y) ((index_t)(((x) | ((y) << (k)->sizeb))))
struct ctx {
unsigned int sizeb, size, size2;
unsigned int gauss_radius;
unsigned int gauss_middle;
uint64_t gauss[MAX_SIZE2];
index_t randomat[MAX_SIZE2];
bool calcmat[MAX_SIZE2];
uint64_t gaussmat[MAX_SIZE2];
index_t unimat[MAX_SIZE2];
AVLFG avlfg;
};
static void makegauss(struct ctx *k, unsigned int sizeb)
{
assert(sizeb >= 1 && sizeb <= MAX_SIZEB);
memset(k, 0, sizeof(*k));
av_lfg_init(&k->avlfg, 123);
k->sizeb = sizeb;
k->size = 1 << k->sizeb;
k->size2 = k->size * k->size;
k->gauss_radius = k->size / 2 - 1;
k->gauss_middle = XY(k, k->gauss_radius, k->gauss_radius);
unsigned int gauss_size = k->gauss_radius * 2 + 1;
unsigned int gauss_size2 = gauss_size * gauss_size;
for (index_t c = 0; c < k->size2; c++)
k->gauss[c] = 0;
double sigma = -log(1.5 / UINT64_MAX * gauss_size2) / k->gauss_radius;
for (index_t gy = 0; gy <= k->gauss_radius; gy++) {
for (index_t gx = 0; gx <= gy; gx++) {
int cx = (int)gx - k->gauss_radius;
int cy = (int)gy - k->gauss_radius;
int sq = cx * cx + cy * cy;
double e = exp(-sqrt(sq) * sigma);
uint64_t v = e / gauss_size2 * UINT64_MAX;
k->gauss[XY(k, gx, gy)] =
k->gauss[XY(k, gy, gx)] =
k->gauss[XY(k, gx, gauss_size - 1 - gy)] =
k->gauss[XY(k, gy, gauss_size - 1 - gx)] =
k->gauss[XY(k, gauss_size - 1 - gx, gy)] =
k->gauss[XY(k, gauss_size - 1 - gy, gx)] =
k->gauss[XY(k, gauss_size - 1 - gx, gauss_size - 1 - gy)] =
k->gauss[XY(k, gauss_size - 1 - gy, gauss_size - 1 - gx)] = v;
}
}
uint64_t total = 0;
for (index_t c = 0; c < k->size2; c++) {
uint64_t oldtotal = total;
total += k->gauss[c];
assert(total >= oldtotal);
}
}
static void setbit(struct ctx *k, index_t c)
{
if (k->calcmat[c])
return;
k->calcmat[c] = true;
uint64_t *m = k->gaussmat;
uint64_t *me = k->gaussmat + k->size2;
uint64_t *g = k->gauss + WRAP_SIZE2(k, k->gauss_middle + k->size2 - c);
uint64_t *ge = k->gauss + k->size2;
while (g < ge)
*m++ += *g++;
g = k->gauss;
while (m < me)
*m++ += *g++;
}
static index_t getmin(struct ctx *k)
{
uint64_t min = UINT64_MAX;
index_t resnum = 0;
unsigned int size2 = k->size2;
for (index_t c = 0; c < size2; c++) {
if (k->calcmat[c])
continue;
uint64_t total = k->gaussmat[c];
if (total <= min) {
if (total != min) {
min = total;
resnum = 0;
}
k->randomat[resnum++] = c;
}
}
if (resnum == 1)
return k->randomat[0];
if (resnum == size2)
return size2 / 2;
return k->randomat[av_lfg_get(&k->avlfg) % resnum];
}
static void makeuniform(struct ctx *k)
{
unsigned int size2 = k->size2;
for (index_t c = 0; c < size2; c++) {
index_t r = getmin(k);
setbit(k, r);
k->unimat[r] = c;
}
}
// out_matrix is a reactangular tsize * tsize array, where tsize = (1 << size).
void mp_make_fruit_dither_matrix(float *out_matrix, int size)
{
struct ctx *k = talloc(NULL, struct ctx);
makegauss(k, size);
makeuniform(k);
float invscale = k->size2;
for(index_t y = 0; y < k->size; y++) {
for(index_t x = 0; x < k->size; x++)
out_matrix[x + y * k->size] = k->unimat[XY(k, x, y)] / invscale;
}
talloc_free(k);
}
void mp_make_ordered_dither_matrix(unsigned char *m, int size)
{
m[0] = 0;
for (int sz = 1; sz < size; sz *= 2) {
int offset[] = {sz*size, sz, sz * (size+1), 0};
for (int i = 0; i < 4; i++)
for (int y = 0; y < sz * size; y += size)
for (int x = 0; x < sz; x++)
m[x+y+offset[i]] = m[x+y] * 4 + (3-i) * 256/size/size;
}
}
#if 0
static int index_cmp(const void *a, const void *b)
{
index_t x = *(const index_t *)a;
index_t y = *(const index_t *)b;
return x < y ? -1 : x > y;
}
static void fsck(struct ctx *k)
{
qsort(k->unimat, k->size2, sizeof k->unimat[0], index_cmp);
for (index_t c = 0; c < k->size2; c++)
assert(k->unimat[c] == c);
}
uint16_t r[MAX_SIZE2];
static void print(struct ctx *k)
{
#if 0
puts("#include <stdint.h>");
printf("static const int mp_dither_size = %d;\n", k->size);
printf("static const int mp_dither_size2 = %d;\n", k->size2);
printf("static const uint16_t mp_dither_matrix[] = {\n");
for(index_t y = 0; y < k->size; y++) {
printf("\t");
for(index_t x = 0; x < k->size; x++)
printf("%4"PRIuFAST32", ", k->unimat[XY(k, x, y)]);
printf("\n");
}
puts("};");
#else
for(index_t y = 0; y < k->size; y++) {
for(index_t x = 0; x < k->size; x++)
r[XY(k, x, y)] = k->unimat[XY(k, x, y)];
}
#endif
}
#include "osdep/timer.h"
int main(void)
{
mp_time_init();
struct ctx *k = malloc(sizeof(struct ctx));
int64_t s = mp_time_us();
makegauss(k, 6);
makeuniform(k);
print(k);
fsck(k);
int64_t l = mp_time_us() - s;
printf("time: %f ms\n", l / 1000.0);
return 0;
}
#endif