| Dees_Troy | 51a0e82 | 2012-09-05 15:24:24 -0400 | [diff] [blame] | 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[])); |