1 /* 2 * reserved comment block 3 * DO NOT REMOVE OR ALTER! 4 */ 5 /* 6 * jchuff.h 7 * 8 * Copyright (C) 1991-1997, Thomas G. Lane. 9 * This file is part of the Independent JPEG Group's software. 10 * For conditions of distribution and use, see the accompanying README file. 11 * 12 * This file contains declarations for Huffman entropy encoding routines 13 * that are shared between the sequential encoder (jchuff.c) and the 14 * progressive encoder (jcphuff.c). No other modules need to see these. 15 */ 16 17 /* The legal range of a DCT coefficient is 18 * -1024 .. +1023 for 8-bit data; 19 * -16384 .. +16383 for 12-bit data. 20 * Hence the magnitude should always fit in 10 or 14 bits respectively. 21 */ 22 23 #if BITS_IN_JSAMPLE == 8 24 #define MAX_COEF_BITS 10 25 #else 26 #define MAX_COEF_BITS 14 27 #endif 28 29 /* Derived data constructed for each Huffman table */ 30 31 typedef struct { 32 unsigned int ehufco[256]; /* code for each symbol */ 33 char ehufsi[256]; /* length of code for each symbol */ 34 /* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */ 35 } c_derived_tbl; 36 37 /* Short forms of external names for systems with brain-damaged linkers. */ 38 39 #ifdef NEED_SHORT_EXTERNAL_NAMES 40 #define jpeg_make_c_derived_tbl jMkCDerived 41 #define jpeg_gen_optimal_table jGenOptTbl 42 #endif /* NEED_SHORT_EXTERNAL_NAMES */ 43 44 /* Expand a Huffman table definition into the derived format */ 45 EXTERN(void) jpeg_make_c_derived_tbl 46 JPP((j_compress_ptr cinfo, boolean isDC, int tblno, 47 c_derived_tbl ** pdtbl)); 48 49 /* Generate an optimal table definition given the specified counts */ 50 EXTERN(void) jpeg_gen_optimal_table 51 JPP((j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[])); 52