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jchuff.h
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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[]));
c_derived_tbl
Definition: jchuff.h:27
pdtbl
boolean int c_derived_tbl ** pdtbl
Definition: jchuff.h:42
freq
JHUFF_TBL long freq[]
Definition: jchuff.h:47
jpeg_make_c_derived_tbl
jpeg_make_c_derived_tbl(j_compress_ptr cinfo, boolean isDC, int tblno, c_derived_tbl **pdtbl)
Definition: jchuff.c:179
JPP
#define JPP(arglist)
Definition: jpeglib.h:818
jpeg_compress_struct
Definition: jpeglib.h:268
EXTERN
EXTERN(void) jpeg_make_c_derived_tbl JPP((j_compress_ptr cinfo
jpeg_gen_optimal_table
jpeg_gen_optimal_table(j_compress_ptr cinfo, JHUFF_TBL *htbl, long freq[])
Definition: jchuff.c:705
htbl
JHUFF_TBL * htbl
Definition: jchuff.h:47
JHUFF_TBL
Definition: jpeglib.h:100
tblno
boolean int tblno
Definition: jchuff.h:42
isDC
boolean isDC
Definition: jchuff.h:42