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. */ 61 typedef 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 */ 69 void 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 */ 75 void ff_big_div(BigInt *b, uint8_t a, uint8_t *r); 76 77 /** 78 * Multiply a by b storing the result in b. 79 */ 80 void 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 */ 85 enum 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. */ 90 typedef struct { 91 uint8_t range; 92 uint8_t offset; 93 } ProbRange; 94 95 extern const ProbRange ff_xface_probranges_per_level[4][3]; 96 97 extern const ProbRange ff_xface_probranges_2x2[16]; 98 99 void ff_xface_generate_face(uint8_t *dst, uint8_t * const src); 100 101 #endif /* AVCODEC_XFACE_H */ 102