1 /* 2 * jchuff.h 3 * 4 * This file was part of the Independent JPEG Group's software: 5 * Copyright (C) 1991-1997, Thomas G. Lane. 6 * It was modified by The libjpeg-turbo Project to include only code relevant 7 * to libjpeg-turbo. 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 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 27 /* Derived data constructed for each Huffman table */ 28 29 typedef struct { 30 unsigned int ehufco[256]; /* code for each symbol */ 31 char ehufsi[256]; /* length of code for each symbol */ 32 /* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */ 33 } c_derived_tbl; 34 35 /* Expand a Huffman table definition into the derived format */ 36 EXTERN(void) jpeg_make_c_derived_tbl 37 (j_compress_ptr cinfo, boolean isDC, int tblno, 38 c_derived_tbl ** pdtbl); 39 40 /* Generate an optimal table definition given the specified counts */ 41 EXTERN(void) jpeg_gen_optimal_table 42 (j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[]); 43
