kc3-lang/libjpeg-turbo/jlossls.h

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• Hash : af618ffe
  Author :
  Date : 2022-11-08T15:01:18
  

  Clean up the lossless JPEG feature
  
  - Rename jpeg_simple_lossless() to jpeg_enable_lossless() and modify the
    function so that it stores the lossless parameters directly in the Ss
    and Al fields of jpeg_compress_struct rather than using a scan script.
  
  - Move the cjpeg -lossless switch into "Switches for advanced users".
  
  - Document the libjpeg API and run-time features that are unavailable in
    lossless mode, and ensure that all parameters, functions, and switches
    related to unavailable features are ignored or generate errors in
    lossless mode.
  
  - Defer any action that depends on whether lossless mode is enabled
    until jpeg_start_compress()/jpeg_start_decompress() is called.
  
  - Document the purpose of the point transform value.
  
  - "Codec" stands for coder/decoder, so it is a bit awkward to say
    "lossless compression codec" and "lossless decompression codec".
    Use "lossless compressor" and "lossless decompressor" instead.
  
  - Restore backward API/ABI compatibility with libjpeg v6b:
  
    * Move the new 'lossless' field from the exposed jpeg_compress_struct
      and jpeg_decompress_struct structures into the opaque
      jpeg_comp_master and jpeg_decomp_master structures, and allocate the
      master structures in the body of jpeg_create_compress() and
      jpeg_create_decompress().
  
    * Remove the new 'process' field from jpeg_compress_struct and
      jpeg_decompress_struct and replace it with the old
      'progressive_mode' field and the new 'lossless' field.
  
    * Remove the new 'data_unit' field from jpeg_compress_struct and
      jpeg_decompress_struct and replace it with a locally-computed
      data unit variable.
  
    * Restore the names of macros and fields that refer to DCT blocks, and
      document that they have a different meaning in lossless mode.  (Most
      of them aren't very meaningful in lossless mode anyhow.)
  
    * Remove the new alloc_darray() method from jpeg_memory_mgr and
      replace it with an internal macro that wraps the alloc_sarray()
      method.
  
    * Move the JDIFF* data types from jpeglib.h and jmorecfg.h into
      jpegint.h.
  
    * Remove the new 'codec' field from jpeg_compress_struct and
      jpeg_decompress_struct and instead reuse the existing internal
      coefficient control, forward/inverse DCT, and entropy
      encoding/decoding structures for lossless compression/decompression.
  
    * Repurpose existing error codes rather than introducing new ones.
      (The new JERR_BAD_RESTART and JWRN_MUST_DOWNSCALE codes remain,
      although JWRN_MUST_DOWNSCALE will probably be removed in
      libjpeg-turbo, since we have a different way of handling multiple
      data precisions.)
  
  - Automatically enable lossless mode when a scan script with parameters
    that are only valid for lossless mode is detected, and document the
    use of scan scripts to generate lossless JPEG images.
  
  - Move the sequential and shared Huffman routines back into jchuff.c and
    jdhuff.c, and document that those routines are shared with jclhuff.c
    and jdlhuff.c as well as with jcphuff.c and jdphuff.c.
  
  - Move MAX_DIFF_BITS from jchuff.h into jclhuff.c, the only place where
    it is used.
  
  - Move the predictor and scaler code into jclossls.c and jdlossls.c.
  
  - Streamline register usage in the [un]differencers (inspired by similar
    optimizations in the color [de]converters.)
  
  - Restructure the logic in a few places to reduce duplicated code.
  
  - Ensure that all lossless-specific code is guarded by
    C_LOSSLESS_SUPPORTED or D_LOSSLESS_SUPPORTED and that the library can
    be built successfully if either or both of those macros is undefined.
  
  - Remove all short forms of external names introduced by the lossless
    JPEG patch.  (These will not be needed by libjpeg-turbo, so there is
    no use cleaning them up.)
  
  - Various wordsmithing, formatting, and punctuation tweaks
  
  - Eliminate various compiler warnings.
  

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• jlossls.h

• /*
   * jlossls.h
   *
   * This file was part of the Independent JPEG Group's software:
   * Copyright (C) 1998, Thomas G. Lane.
   * Lossless JPEG Modifications:
   * Copyright (C) 1999, Ken Murchison.
   * libjpeg-turbo Modifications:
   * Copyright (C) 2022, D. R. Commander.
   * For conditions of distribution and use, see the accompanying README.ijg
   * file.
   *
   * This include file contains common declarations for the lossless JPEG
   * codec modules.
   */
  
  #ifndef JLOSSLS_H
  #define JLOSSLS_H
  
  #if defined(C_LOSSLESS_SUPPORTED) || defined(D_LOSSLESS_SUPPORTED)
  
  #define JPEG_INTERNALS
  #include "jpeglib.h"
  #include "jsamplecomp.h"
  
  
  #define ALLOC_DARRAY(pool_id, diffsperrow, numrows) \
    (JDIFFARRAY)(*cinfo->mem->alloc_sarray) \
      ((j_common_ptr)cinfo, pool_id, \
       (diffsperrow) * sizeof(JDIFF) / sizeof(_JSAMPLE), numrows)
  
  
  /*
   * Table H.1: Predictors for lossless coding.
   */
  
  #define PREDICTOR1  Ra
  #define PREDICTOR2  Rb
  #define PREDICTOR3  Rc
  #define PREDICTOR4  (int)((JLONG)Ra + (JLONG)Rb - (JLONG)Rc)
  #define PREDICTOR5  (int)((JLONG)Ra + RIGHT_SHIFT((JLONG)Rb - (JLONG)Rc, 1))
  #define PREDICTOR6  (int)((JLONG)Rb + RIGHT_SHIFT((JLONG)Ra - (JLONG)Rc, 1))
  #define PREDICTOR7  (int)RIGHT_SHIFT((JLONG)Ra + (JLONG)Rb, 1)
  
  #endif
  
  
  #ifdef C_LOSSLESS_SUPPORTED
  
  typedef void (*predict_difference_method_ptr) (j_compress_ptr cinfo, int ci,
                                                 _JSAMPROW input_buf,
                                                 _JSAMPROW prev_row,
                                                 JDIFFROW diff_buf,
                                                 JDIMENSION width);
  
  /* Lossless compressor */
  typedef struct {
    struct jpeg_forward_dct pub;  /* public fields */
  
    /* It is useful to allow each component to have a separate diff method. */
    predict_difference_method_ptr predict_difference[MAX_COMPONENTS];
  
    /* MCU rows left in the restart interval for each component */
    unsigned int restart_rows_to_go[MAX_COMPONENTS];
  
    /* Sample scaling */
    void (*scaler_scale) (j_compress_ptr cinfo, _JSAMPROW input_buf,
                          _JSAMPROW output_buf, JDIMENSION width);
  } jpeg_lossless_compressor;
  
  typedef jpeg_lossless_compressor *lossless_comp_ptr;
  
  #endif /* C_LOSSLESS_SUPPORTED */
  
  
  #ifdef D_LOSSLESS_SUPPORTED
  
  typedef void (*predict_undifference_method_ptr) (j_decompress_ptr cinfo,
                                                   int comp_index,
                                                   JDIFFROW diff_buf,
                                                   JDIFFROW prev_row,
                                                   JDIFFROW undiff_buf,
                                                   JDIMENSION width);
  
  /* Lossless decompressor */
  typedef struct {
    struct jpeg_inverse_dct pub;  /* public fields */
  
    /* It is useful to allow each component to have a separate undiff method. */
    predict_undifference_method_ptr predict_undifference[MAX_COMPONENTS];
  
    /* Sample scaling */
    void (*scaler_scale) (j_decompress_ptr cinfo, JDIFFROW diff_buf,
                          _JSAMPROW output_buf, JDIMENSION width);
  } jpeg_lossless_decompressor;
  
  typedef jpeg_lossless_decompressor *lossless_decomp_ptr;
  
  #endif /* D_LOSSLESS_SUPPORTED */
  
  #endif /* JLOSSLS_H */
  

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