Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 1 | /* |
| 2 | * jchuff.h |
| 3 | * |
DRC | 5033f3e | 2014-05-18 18:33:44 +0000 | [diff] [blame] | 4 | * This file was part of the Independent JPEG Group's software: |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 5 | * Copyright (C) 1991-1997, Thomas G. Lane. |
DRC | 5033f3e | 2014-05-18 18:33:44 +0000 | [diff] [blame] | 6 | * It was modified by The libjpeg-turbo Project to include only code relevant |
| 7 | * to libjpeg-turbo. |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 8 | * For conditions of distribution and use, see the accompanying README file. |
| 9 | * |
| 10 | * This file contains declarations for Huffman entropy encoding routines |
| 11 | * that are shared between the sequential encoder (jchuff.c) and the |
| 12 | * progressive encoder (jcphuff.c). No other modules need to see these. |
| 13 | */ |
| 14 | |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 15 | /* The legal range of a DCT coefficient is |
| 16 | * -1024 .. +1023 for 8-bit data; |
| 17 | * -16384 .. +16383 for 12-bit data. |
| 18 | * Hence the magnitude should always fit in 10 or 14 bits respectively. |
| 19 | */ |
| 20 | |
| 21 | #if BITS_IN_JSAMPLE == 8 |
| 22 | #define MAX_COEF_BITS 10 |
| 23 | #else |
| 24 | #define MAX_COEF_BITS 14 |
| 25 | #endif |
| 26 | |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 27 | /* Derived data constructed for each Huffman table */ |
| 28 | |
| 29 | typedef struct { |
DRC | e5eaf37 | 2014-05-09 18:00:32 +0000 | [diff] [blame] | 30 | unsigned int ehufco[256]; /* code for each symbol */ |
| 31 | char ehufsi[256]; /* length of code for each symbol */ |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 32 | /* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */ |
| 33 | } c_derived_tbl; |
| 34 | |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 35 | /* Expand a Huffman table definition into the derived format */ |
Thomas G. Lane | 489583f | 1996-02-07 00:00:00 +0000 | [diff] [blame] | 36 | EXTERN(void) jpeg_make_c_derived_tbl |
DRC | bc56b75 | 2014-05-16 10:43:44 +0000 | [diff] [blame] | 37 | (j_compress_ptr cinfo, boolean isDC, int tblno, |
| 38 | c_derived_tbl ** pdtbl); |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 39 | |
| 40 | /* Generate an optimal table definition given the specified counts */ |
Thomas G. Lane | 489583f | 1996-02-07 00:00:00 +0000 | [diff] [blame] | 41 | EXTERN(void) jpeg_gen_optimal_table |
DRC | bc56b75 | 2014-05-16 10:43:44 +0000 | [diff] [blame] | 42 | (j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[]); |