1/* 2 * Copyright (c) 1990 James Ashton - Sydney University 3 * Copyright (c) 2012 Stefano Sabatini 4 * 5 * This file is part of FFmpeg. 6 * 7 * FFmpeg is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU Lesser General Public 9 * License as published by the Free Software Foundation; either 10 * version 2.1 of the License, or (at your option) any later version. 11 * 12 * FFmpeg is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 * Lesser General Public License for more details. 16 * 17 * You should have received a copy of the GNU Lesser General Public 18 * License along with FFmpeg; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 20 */ 21 22/** 23 * @file 24 * X-Face common definitions. 25 */ 26 27#include <stdint.h> 28 29/* define the face size - 48x48x1 */ 30#define XFACE_WIDTH 48 31#define XFACE_HEIGHT 48 32#define XFACE_PIXELS (XFACE_WIDTH * XFACE_HEIGHT) 33 34/* compressed output uses the full range of printable characters. 35 * In ASCII these are in a contiguous block so we just need to know 36 * the first and last. The total number of printables is needed too. */ 37#define XFACE_FIRST_PRINT '!' 38#define XFACE_LAST_PRINT '~' 39#define XFACE_PRINTS (XFACE_LAST_PRINT - XFACE_FIRST_PRINT + 1) 40 41/* 42 * Image is encoded as a big integer, using characters from '~' to 43 * '!', for a total of 92 symbols. In order to express 48x48=2304 44 * bits, we need a total of 354 digits, as given by: 45 * ceil(lg_92(2^2304)) = 354 46 */ 47#define XFACE_MAX_DIGITS 354 48 49#define XFACE_BITSPERWORD 8 50#define XFACE_WORDCARRY (1 << XFACE_BITSPERWORD) 51#define XFACE_WORDMASK (XFACE_WORDCARRY - 1) 52 53#define XFACE_MAX_WORDS ((XFACE_PIXELS * 2 + XFACE_BITSPERWORD - 1) / XFACE_BITSPERWORD) 54 55/* Portable, very large unsigned integer arithmetic is needed. 56 * Implementation uses arrays of WORDs. */ 57typedef struct { 58 int nb_words; 59 uint8_t words[XFACE_MAX_WORDS]; 60} BigInt; 61 62/** 63 * Add a to b storing the result in b. 64 */ 65void ff_big_add(BigInt *b, uint8_t a); 66 67/** 68 * Divide b by a storing the result in b and the remainder in the word 69 * pointed to by r. 70 */ 71void ff_big_div(BigInt *b, uint8_t a, uint8_t *r); 72 73/** 74 * Multiply a by b storing the result in b. 75 */ 76void ff_big_mul(BigInt *b, uint8_t a); 77 78/* Each face is encoded using 9 octrees of 16x16 each. Each level of the 79 * trees has varying probabilities of being white, grey or black. 80 * The table below is based on sampling many faces */ 81enum XFaceColor { XFACE_COLOR_BLACK = 0, XFACE_COLOR_GREY, XFACE_COLOR_WHITE }; 82 83/* Data of varying probabilities are encoded by a value in the range 0 - 255. 84 * The probability of the data determines the range of possible encodings. 85 * Offset gives the first possible encoding of the range. */ 86typedef struct { 87 int range; 88 int offset; 89} ProbRange; 90 91extern const ProbRange ff_xface_probranges_per_level[4][3]; 92 93extern const ProbRange ff_xface_probranges_2x2[16]; 94 95void ff_xface_generate_face(uint8_t *dst, uint8_t * const src); 96