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.ijg 9 * file. 10 * 11 * This file contains declarations for Huffman entropy encoding routines 12 * that are shared between the sequential encoder (jchuff.c) and the 13 * progressive encoder (jcphuff.c). No other modules need to see these. 14 */ 15 16 /* The legal range of a DCT coefficient is 17 * -1024 .. +1023 for 8-bit data; 18 * -16384 .. +16383 for 12-bit data. 19 * Hence the magnitude should always fit in 10 or 14 bits respectively. 20 */ 21 22 #if BITS_IN_JSAMPLE == 8 23 #define MAX_COEF_BITS 10 24 #else 25 #define MAX_COEF_BITS 14 26 #endif 27 28 /* Derived data constructed for each Huffman table */ 29 30 typedef struct { 31 unsigned int ehufco[256]; /* code for each symbol */ 32 char ehufsi[256]; /* length of code for each symbol */ 33 /* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */ 34 } c_derived_tbl; 35 36 /* Expand a Huffman table definition into the derived format */ 37 EXTERN(void) jpeg_make_c_derived_tbl 38 (j_compress_ptr cinfo, boolean isDC, int tblno, 39 c_derived_tbl ** pdtbl); 40 41 /* Generate an optimal table definition given the specified counts */ 42 EXTERN(void) jpeg_gen_optimal_table 43 (j_compress_ptr cinfo, JHUFF_TBL *htbl, long freq[]); 44
