mirror of
https://git.ffmpeg.org/ffmpeg.git
synced 2024-12-29 10:52:20 +00:00
cd559bb49a
Based on libcompface code by James Ashton <James.Ashton@anu.edu.au>, and relicensed to LGPL with the author's consent.
96 lines
3.0 KiB
C
96 lines
3.0 KiB
C
/*
|
|
* Copyright (c) 1990 James Ashton - Sydney University
|
|
* Copyright (c) 2012 Stefano Sabatini
|
|
*
|
|
* 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
|
|
*/
|
|
|
|
/**
|
|
* @file
|
|
* X-Face common definitions.
|
|
*/
|
|
|
|
#include <stdint.h>
|
|
|
|
/* define the face size - 48x48x1 */
|
|
#define XFACE_WIDTH 48
|
|
#define XFACE_HEIGHT 48
|
|
#define XFACE_PIXELS (XFACE_WIDTH * XFACE_HEIGHT)
|
|
|
|
/* compressed output uses the full range of printable characters.
|
|
* In ASCII these are in a contiguous block so we just need to know
|
|
* the first and last. The total number of printables is needed too. */
|
|
#define XFACE_FIRST_PRINT '!'
|
|
#define XFACE_LAST_PRINT '~'
|
|
#define XFACE_PRINTS (XFACE_LAST_PRINT - XFACE_FIRST_PRINT + 1)
|
|
|
|
/*
|
|
* Image is encoded as a big integer, using characters from '~' to
|
|
* '!', for a total of 92 symbols. In order to express 48x48=2304
|
|
* bits, we need a total of 354 digits, as given by:
|
|
* ceil(lg_92(2^2304)) = 354
|
|
*/
|
|
#define XFACE_MAX_DIGITS 354
|
|
|
|
#define XFACE_BITSPERWORD 8
|
|
#define XFACE_WORDCARRY (1 << XFACE_BITSPERWORD)
|
|
#define XFACE_WORDMASK (XFACE_WORDCARRY - 1)
|
|
|
|
#define XFACE_MAX_WORDS ((XFACE_PIXELS * 2 + XFACE_BITSPERWORD - 1) / XFACE_BITSPERWORD)
|
|
|
|
/* Portable, very large unsigned integer arithmetic is needed.
|
|
* Implementation uses arrays of WORDs. */
|
|
typedef struct {
|
|
int nb_words;
|
|
uint8_t words[XFACE_MAX_WORDS];
|
|
} BigInt;
|
|
|
|
/**
|
|
* Add a to b storing the result in b.
|
|
*/
|
|
void ff_big_add(BigInt *b, uint8_t a);
|
|
|
|
/**
|
|
* Divide b by a storing the result in b and the remainder in the word
|
|
* pointed to by r.
|
|
*/
|
|
void ff_big_div(BigInt *b, uint8_t a, uint8_t *r);
|
|
|
|
/**
|
|
* Multiply a by b storing the result in b.
|
|
*/
|
|
void ff_big_mul(BigInt *b, uint8_t a);
|
|
|
|
/* Each face is encoded using 9 octrees of 16x16 each. Each level of the
|
|
* trees has varying probabilities of being white, grey or black.
|
|
* The table below is based on sampling many faces */
|
|
enum XFaceColor { XFACE_COLOR_BLACK = 0, XFACE_COLOR_GREY, XFACE_COLOR_WHITE };
|
|
|
|
/* Data of varying probabilities are encoded by a value in the range 0 - 255.
|
|
* The probability of the data determines the range of possible encodings.
|
|
* Offset gives the first possible encoding of the range. */
|
|
typedef struct {
|
|
int range;
|
|
int offset;
|
|
} ProbRange;
|
|
|
|
extern const ProbRange ff_xface_probranges_per_level[4][3];
|
|
|
|
extern const ProbRange ff_xface_probranges_2x2[16];
|
|
|
|
void ff_xface_generate_face(uint8_t *dst, uint8_t * const src);
|