/* | |
* jchuff.h | |
* | |
* Copyright (C) 1991-1997, Thomas G. Lane. | |
* This file is part of the Independent JPEG Group's software. | |
* For conditions of distribution and use, see the accompanying README file. | |
* | |
* This file contains declarations for Huffman entropy encoding routines | |
* that are shared between the sequential encoder (jchuff.c) and the | |
* progressive encoder (jcphuff.c). No other modules need to see these. | |
*/ | |
/* The legal range of a DCT coefficient is | |
* -1024 .. +1023 for 8-bit data; | |
* -16384 .. +16383 for 12-bit data. | |
* Hence the magnitude should always fit in 10 or 14 bits respectively. | |
*/ | |
#if BITS_IN_JSAMPLE == 8 | |
#define MAX_COEF_BITS 10 | |
#else | |
#define MAX_COEF_BITS 14 | |
#endif | |
/* Derived data constructed for each Huffman table */ | |
typedef struct { | |
unsigned int ehufco[256]; /* code for each symbol */ | |
char ehufsi[256]; /* length of code for each symbol */ | |
/* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */ | |
} c_derived_tbl; | |
/* Short forms of external names for systems with brain-damaged linkers. */ | |
#ifdef NEED_SHORT_EXTERNAL_NAMES | |
#define jpeg_make_c_derived_tbl jMkCDerived | |
#define jpeg_gen_optimal_table jGenOptTbl | |
#endif /* NEED_SHORT_EXTERNAL_NAMES */ | |
/* Expand a Huffman table definition into the derived format */ | |
EXTERN(void) jpeg_make_c_derived_tbl | |
JPP((j_compress_ptr cinfo, boolean isDC, int tblno, | |
c_derived_tbl ** pdtbl)); | |
/* Generate an optimal table definition given the specified counts */ | |
EXTERN(void) jpeg_gen_optimal_table | |
JPP((j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[])); |