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