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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. */ | |
57 | typedef 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 | */ | |
65 | void 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 | */ | |
71 | void ff_big_div(BigInt *b, uint8_t a, uint8_t *r); | |
72 | ||
73 | /** | |
74 | * Multiply a by b storing the result in b. | |
75 | */ | |
76 | void 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 */ | |
81 | enum 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. */ | |
86 | typedef struct { | |
87 | int range; | |
88 | int offset; | |
89 | } ProbRange; | |
90 | ||
91 | extern const ProbRange ff_xface_probranges_per_level[4][3]; | |
92 | ||
93 | extern const ProbRange ff_xface_probranges_2x2[16]; | |
94 | ||
95 | void ff_xface_generate_face(uint8_t *dst, uint8_t * const src); |