| 1 | /* |
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| 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 | |
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| 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 | |
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| 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 | |
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| 25 | /* Derived data constructed for each Huffman table */ |
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| 26 | |
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| 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 | |
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| 33 | /* Short forms of external names for systems with brain-damaged linkers. */ |
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| 34 | |
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| 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 | |
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| 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 | |
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| 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[])); |
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