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#ifndef AVCODEC_XFACE_H 28#define AVCODEC_XFACE_H 29 30#include <stdint.h> 31 32/* define the face size - 48x48x1 */ 33#define XFACE_WIDTH 48 34#define XFACE_HEIGHT 48 35#define XFACE_PIXELS (XFACE_WIDTH * XFACE_HEIGHT) 36 37/* compressed output uses the full range of printable characters. 38 * In ASCII these are in a contiguous block so we just need to know 39 * the first and last. The total number of printables is needed too. */ 40#define XFACE_FIRST_PRINT '!' 41#define XFACE_LAST_PRINT '~' 42#define XFACE_PRINTS (XFACE_LAST_PRINT - XFACE_FIRST_PRINT + 1) 43 44/* 45 * Image is encoded as a big integer, using characters from '~' to 46 * '!', for a total of 94 symbols. In order to express 47 * 48x48 pixels with the worst case encoding 666 symbols should 48 * be sufficient. 49 */ 50#define XFACE_MAX_DIGITS 666 51 52#define XFACE_BITSPERWORD 8 53#define XFACE_WORDCARRY (1 << XFACE_BITSPERWORD) 54#define XFACE_WORDMASK (XFACE_WORDCARRY - 1) 55 56// This must be larger or equal to log256(94^XFACE_MAX_DIGITS) 57#define XFACE_MAX_WORDS 546 58 59/* Portable, very large unsigned integer arithmetic is needed. 60 * Implementation uses arrays of WORDs. */ 61typedef struct { 62 int nb_words; 63 uint8_t words[XFACE_MAX_WORDS]; 64} BigInt; 65 66/** 67 * Add a to b storing the result in b. 68 */ 69void ff_big_add(BigInt *b, uint8_t a); 70 71/** 72 * Divide b by a storing the result in b and the remainder in the word 73 * pointed to by r. 74 */ 75void ff_big_div(BigInt *b, uint8_t a, uint8_t *r); 76 77/** 78 * Multiply a by b storing the result in b. 79 */ 80void ff_big_mul(BigInt *b, uint8_t a); 81 82/* Each face is encoded using 9 octrees of 16x16 each. Each level of the 83 * trees has varying probabilities of being white, grey or black. 84 * The table below is based on sampling many faces */ 85enum XFaceColor { XFACE_COLOR_BLACK = 0, XFACE_COLOR_GREY, XFACE_COLOR_WHITE }; 86 87/* Data of varying probabilities are encoded by a value in the range 0 - 255. 88 * The probability of the data determines the range of possible encodings. 89 * Offset gives the first possible encoding of the range. */ 90typedef struct { 91 uint8_t range; 92 uint8_t offset; 93} ProbRange; 94 95extern const ProbRange ff_xface_probranges_per_level[4][3]; 96 97extern const ProbRange ff_xface_probranges_2x2[16]; 98 99void ff_xface_generate_face(uint8_t *dst, uint8_t * const src); 100 101#endif /* AVCODEC_XFACE_H */ 102