www.pudn.com > imgport.rar > jchuff.h, change:2008-11-05,size:1622b


/* 
 * 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[]));