jchuff.h

Go to the documentation of this file.

/*
 * 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.
 */
 
#ifndef _jchuff_h_
#define _jchuff_h_
 
#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[]));
 
#endif