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6417 | ashmew2 | 1 | /* |
2 | * jchuff.h |
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3 | * |
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4 | * Copyright (C) 1991-1997, Thomas G. Lane. |
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5 | * This file is part of the Independent JPEG Group's software. |
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6 | * For conditions of distribution and use, see the accompanying README file. |
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7 | * |
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8 | * This file contains declarations for Huffman entropy encoding routines |
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9 | * that are shared between the sequential encoder (jchuff.c) and the |
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10 | * progressive encoder (jcphuff.c). No other modules need to see these. |
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11 | */ |
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12 | |||
13 | /* The legal range of a DCT coefficient is |
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14 | * -1024 .. +1023 for 8-bit data; |
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15 | * -16384 .. +16383 for 12-bit data. |
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16 | * Hence the magnitude should always fit in 10 or 14 bits respectively. |
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17 | */ |
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18 | |||
19 | #if BITS_IN_JSAMPLE == 8 |
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20 | #define MAX_COEF_BITS 10 |
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21 | #else |
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22 | #define MAX_COEF_BITS 14 |
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23 | #endif |
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24 | |||
25 | /* Derived data constructed for each Huffman table */ |
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26 | |||
27 | typedef struct { |
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28 | unsigned int ehufco[256]; /* code for each symbol */ |
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29 | char ehufsi[256]; /* length of code for each symbol */ |
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30 | /* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */ |
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31 | } c_derived_tbl; |
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32 | |||
33 | /* Short forms of external names for systems with brain-damaged linkers. */ |
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34 | |||
35 | #ifdef NEED_SHORT_EXTERNAL_NAMES |
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36 | #define jpeg_make_c_derived_tbl jMkCDerived |
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37 | #define jpeg_gen_optimal_table jGenOptTbl |
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38 | #endif /* NEED_SHORT_EXTERNAL_NAMES */ |
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39 | |||
40 | /* Expand a Huffman table definition into the derived format */ |
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41 | EXTERN(void) jpeg_make_c_derived_tbl |
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42 | JPP((j_compress_ptr cinfo, boolean isDC, int tblno, |
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43 | c_derived_tbl ** pdtbl)); |
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44 | |||
45 | /* Generate an optimal table definition given the specified counts */ |
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46 | EXTERN(void) jpeg_gen_optimal_table |
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47 | JPP((j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[])); |