yading@10: /*
yading@10:  * Copyright (c) 1990 James Ashton - Sydney University
yading@10:  * Copyright (c) 2012 Stefano Sabatini
yading@10:  *
yading@10:  * This file is part of FFmpeg.
yading@10:  *
yading@10:  * FFmpeg is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * FFmpeg is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with FFmpeg; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: 
yading@10: /**
yading@10:  * @file
yading@10:  * X-Face common definitions.
yading@10:  */
yading@10: 
yading@10: #include <stdint.h>
yading@10: 
yading@10: /* define the face size - 48x48x1 */
yading@10: #define XFACE_WIDTH  48
yading@10: #define XFACE_HEIGHT 48
yading@10: #define XFACE_PIXELS (XFACE_WIDTH * XFACE_HEIGHT)
yading@10: 
yading@10: /* compressed output uses the full range of printable characters.
yading@10:  * In ASCII these are in a contiguous block so we just need to know
yading@10:  * the first and last. The total number of printables is needed too. */
yading@10: #define XFACE_FIRST_PRINT '!'
yading@10: #define XFACE_LAST_PRINT '~'
yading@10: #define XFACE_PRINTS (XFACE_LAST_PRINT - XFACE_FIRST_PRINT + 1)
yading@10: 
yading@10: /*
yading@10:  * Image is encoded as a big integer, using characters from '~' to
yading@10:  * '!', for a total of 92 symbols. In order to express 48x48=2304
yading@10:  * bits, we need a total of 354 digits, as given by:
yading@10:  * ceil(lg_92(2^2304)) = 354
yading@10:  */
yading@10: #define XFACE_MAX_DIGITS 354
yading@10: 
yading@10: #define XFACE_BITSPERWORD 8
yading@10: #define XFACE_WORDCARRY (1 << XFACE_BITSPERWORD)
yading@10: #define XFACE_WORDMASK (XFACE_WORDCARRY - 1)
yading@10: 
yading@10: #define XFACE_MAX_WORDS ((XFACE_PIXELS * 2 + XFACE_BITSPERWORD - 1) / XFACE_BITSPERWORD)
yading@10: 
yading@10: /* Portable, very large unsigned integer arithmetic is needed.
yading@10:  * Implementation uses arrays of WORDs. */
yading@10: typedef struct {
yading@10:     int nb_words;
yading@10:     uint8_t words[XFACE_MAX_WORDS];
yading@10: } BigInt;
yading@10: 
yading@10: /**
yading@10:  * Add a to b storing the result in b.
yading@10:  */
yading@10: void ff_big_add(BigInt *b, uint8_t a);
yading@10: 
yading@10: /**
yading@10:  * Divide b by a storing the result in b and the remainder in the word
yading@10:  * pointed to by r.
yading@10:  */
yading@10: void ff_big_div(BigInt *b, uint8_t a, uint8_t *r);
yading@10: 
yading@10: /**
yading@10:  * Multiply a by b storing the result in b.
yading@10:  */
yading@10: void ff_big_mul(BigInt *b, uint8_t a);
yading@10: 
yading@10: /* Each face is encoded using 9 octrees of 16x16 each. Each level of the
yading@10:  * trees has varying probabilities of being white, grey or black.
yading@10:  * The table below is based on sampling many faces */
yading@10: enum XFaceColor { XFACE_COLOR_BLACK = 0, XFACE_COLOR_GREY, XFACE_COLOR_WHITE };
yading@10: 
yading@10: /* Data of varying probabilities are encoded by a value in the range 0 - 255.
yading@10:  * The probability of the data determines the range of possible encodings.
yading@10:  * Offset gives the first possible encoding of the range. */
yading@10: typedef struct {
yading@10:     int range;
yading@10:     int offset;
yading@10: } ProbRange;
yading@10: 
yading@10: extern const ProbRange ff_xface_probranges_per_level[4][3];
yading@10: 
yading@10: extern const ProbRange ff_xface_probranges_2x2[16];
yading@10: 
yading@10: void ff_xface_generate_face(uint8_t *dst, uint8_t * const src);