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🎥 Command line media player
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C
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176/* * 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 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. * * 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 Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with mpv. If not, see <http://www.gnu.org/licenses/>. */
#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 "mpv_talloc.h"#include "dither.h"
#define MAX_SIZEB 8#define MAX_SIZE (1 << MAX_SIZEB)#define MAX_SIZE2 (MAX_SIZE * MAX_SIZE)
#define WRAP_SIZE2(k, x) ((unsigned int)((unsigned int)(x) & ((k)->size2 - 1)))#define XY(k, x, y) ((unsigned int)(((x) | ((y) << (k)->sizeb))))
struct ctx { unsigned int sizeb, size, size2; unsigned int gauss_radius; unsigned int gauss_middle; uint64_t gauss[MAX_SIZE2]; unsigned int randomat[MAX_SIZE2]; bool calcmat[MAX_SIZE2]; uint64_t gaussmat[MAX_SIZE2]; unsigned int unimat[MAX_SIZE2]; AVLFG avlfg;};
static void makegauss(struct ctx *k, unsigned int sizeb){ assert(sizeb >= 1 && sizeb <= MAX_SIZEB);
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 (unsigned int c = 0; c < k->size2; c++) k->gauss[c] = 0;
double sigma = -log(1.5 / (double) UINT64_MAX * gauss_size2) / k->gauss_radius;
for (unsigned int gy = 0; gy <= k->gauss_radius; gy++) { for (unsigned int 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 * (double) 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 (unsigned int c = 0; c < k->size2; c++) { uint64_t oldtotal = total; total += k->gauss[c]; assert(total >= oldtotal); }}
static void setbit(struct ctx *k, unsigned int 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 unsigned int getmin(struct ctx *k){ uint64_t min = UINT64_MAX; unsigned int resnum = 0; unsigned int size2 = k->size2; for (unsigned int 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 (unsigned int c = 0; c < size2; c++) { unsigned int 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_zero(NULL, struct ctx); makegauss(k, size); makeuniform(k); float invscale = k->size2; for(unsigned int y = 0; y < k->size; y++) { for(unsigned int 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; }}