kc3-lang/libjpeg-turbo/jcapistd.c

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• Hash : b56e8b28
  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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• jcapistd.c

• /*
   * jcapistd.c
   *
   * This file was part of the Independent JPEG Group's software:
   * Copyright (C) 1994-1996, Thomas G. Lane.
   * libjpeg-turbo Modifications:
   * Copyright (C) 2022, D. R. Commander.
   * For conditions of distribution and use, see the accompanying README.ijg
   * file.
   *
   * This file contains application interface code for the compression half
   * of the JPEG library.  These are the "standard" API routines that are
   * used in the normal full-compression case.  They are not used by a
   * transcoding-only application.  Note that if an application links in
   * jpeg_start_compress, it will end up linking in the entire compressor.
   * We thus must separate this file from jcapimin.c to avoid linking the
   * whole compression library into a transcoder.
   */
  
  #define JPEG_INTERNALS
  #include "jinclude.h"
  #include "jpeglib.h"
  #include "jsamplecomp.h"
  
  
  #if BITS_IN_JSAMPLE == 8
  
  /*
   * Compression initialization.
   * Before calling this, all parameters and a data destination must be set up.
   *
   * We require a write_all_tables parameter as a failsafe check when writing
   * multiple datastreams from the same compression object.  Since prior runs
   * will have left all the tables marked sent_table=TRUE, a subsequent run
   * would emit an abbreviated stream (no tables) by default.  This may be what
   * is wanted, but for safety's sake it should not be the default behavior:
   * programmers should have to make a deliberate choice to emit abbreviated
   * images.  Therefore the documentation and examples should encourage people
   * to pass write_all_tables=TRUE; then it will take active thought to do the
   * wrong thing.
   */
  
  GLOBAL(void)
  jpeg_start_compress(j_compress_ptr cinfo, boolean write_all_tables)
  {
    if (cinfo->global_state != CSTATE_START)
      ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  
    if (write_all_tables)
      jpeg_suppress_tables(cinfo, FALSE); /* mark all tables to be written */
  
    /* (Re)initialize error mgr and destination modules */
    (*cinfo->err->reset_error_mgr) ((j_common_ptr)cinfo);
    (*cinfo->dest->init_destination) (cinfo);
    /* Perform master selection of active modules */
    jinit_compress_master(cinfo);
    /* Set up for the first pass */
    (*cinfo->master->prepare_for_pass) (cinfo);
    /* Ready for application to drive first pass through _jpeg_write_scanlines
     * or _jpeg_write_raw_data.
     */
    cinfo->next_scanline = 0;
    cinfo->global_state = (cinfo->raw_data_in ? CSTATE_RAW_OK : CSTATE_SCANNING);
  }
  
  #endif
  
  
  /*
   * Write some scanlines of data to the JPEG compressor.
   *
   * The return value will be the number of lines actually written.
   * This should be less than the supplied num_lines only in case that
   * the data destination module has requested suspension of the compressor,
   * or if more than image_height scanlines are passed in.
   *
   * Note: we warn about excess calls to _jpeg_write_scanlines() since
   * this likely signals an application programmer error.  However,
   * excess scanlines passed in the last valid call are *silently* ignored,
   * so that the application need not adjust num_lines for end-of-image
   * when using a multiple-scanline buffer.
   */
  
  GLOBAL(JDIMENSION)
  _jpeg_write_scanlines(j_compress_ptr cinfo, _JSAMPARRAY scanlines,
                        JDIMENSION num_lines)
  {
    JDIMENSION row_ctr, rows_left;
  
    if (cinfo->data_precision != BITS_IN_JSAMPLE)
      ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
  
    if (cinfo->global_state != CSTATE_SCANNING)
      ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
    if (cinfo->next_scanline >= cinfo->image_height)
      WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
  
    /* Call progress monitor hook if present */
    if (cinfo->progress != NULL) {
      cinfo->progress->pass_counter = (long)cinfo->next_scanline;
      cinfo->progress->pass_limit = (long)cinfo->image_height;
      (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
    }
  
    /* Give master control module another chance if this is first call to
     * _jpeg_write_scanlines.  This lets output of the frame/scan headers be
     * delayed so that application can write COM, etc, markers between
     * jpeg_start_compress and _jpeg_write_scanlines.
     */
    if (cinfo->master->call_pass_startup)
      (*cinfo->master->pass_startup) (cinfo);
  
    /* Ignore any extra scanlines at bottom of image. */
    rows_left = cinfo->image_height - cinfo->next_scanline;
    if (num_lines > rows_left)
      num_lines = rows_left;
  
    row_ctr = 0;
    (*cinfo->main->_process_data) (cinfo, scanlines, &row_ctr, num_lines);
    cinfo->next_scanline += row_ctr;
    return row_ctr;
  }
  
  
  /*
   * Alternate entry point to write raw data.
   * Processes exactly one iMCU row per call, unless suspended.
   */
  
  GLOBAL(JDIMENSION)
  _jpeg_write_raw_data(j_compress_ptr cinfo, _JSAMPIMAGE data,
                       JDIMENSION num_lines)
  {
    JDIMENSION lines_per_iMCU_row;
  
    if (cinfo->data_precision != BITS_IN_JSAMPLE)
      ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
  
    if (cinfo->master->lossless)
      ERREXIT(cinfo, JERR_NOTIMPL);
  
    if (cinfo->global_state != CSTATE_RAW_OK)
      ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
    if (cinfo->next_scanline >= cinfo->image_height) {
      WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
      return 0;
    }
  
    /* Call progress monitor hook if present */
    if (cinfo->progress != NULL) {
      cinfo->progress->pass_counter = (long)cinfo->next_scanline;
      cinfo->progress->pass_limit = (long)cinfo->image_height;
      (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
    }
  
    /* Give master control module another chance if this is first call to
     * _jpeg_write_raw_data.  This lets output of the frame/scan headers be
     * delayed so that application can write COM, etc, markers between
     * jpeg_start_compress and _jpeg_write_raw_data.
     */
    if (cinfo->master->call_pass_startup)
      (*cinfo->master->pass_startup) (cinfo);
  
    /* Verify that at least one iMCU row has been passed. */
    lines_per_iMCU_row = cinfo->max_v_samp_factor * DCTSIZE;
    if (num_lines < lines_per_iMCU_row)
      ERREXIT(cinfo, JERR_BUFFER_SIZE);
  
    /* Directly compress the row. */
    if (!(*cinfo->coef->_compress_data) (cinfo, data)) {
      /* If compressor did not consume the whole row, suspend processing. */
      return 0;
    }
  
    /* OK, we processed one iMCU row. */
    cinfo->next_scanline += lines_per_iMCU_row;
    return lines_per_iMCU_row;
  }
  

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