jchuff.h 1.5 KB

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  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. /* 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. #if BITS_IN_JSAMPLE == 8
  21. #define MAX_COEF_BITS 10
  22. #else
  23. #define MAX_COEF_BITS 14
  24. #endif
  25. /* Derived data constructed for each Huffman table */
  26. typedef struct {
  27. unsigned int ehufco[256]; /* code for each symbol */
  28. char ehufsi[256]; /* length of code for each symbol */
  29. /* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */
  30. } c_derived_tbl;
  31. /* Expand a Huffman table definition into the derived format */
  32. EXTERN(void) jpeg_make_c_derived_tbl(j_compress_ptr cinfo, boolean isDC,
  33. int tblno, c_derived_tbl **pdtbl);
  34. /* Generate an optimal table definition given the specified counts */
  35. EXTERN(void) jpeg_gen_optimal_table(j_compress_ptr cinfo, JHUFF_TBL *htbl,
  36. long freq[]);