/* * 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);