kc3-lang/libjpeg-turbo/jcinit.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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• jcinit.c

• /*
   * jcinit.c
   *
   * This file was part of the Independent JPEG Group's software:
   * Copyright (C) 1991-1997, Thomas G. Lane.
   * Lossless JPEG Modifications:
   * Copyright (C) 1999, Ken Murchison.
   * libjpeg-turbo Modifications:
   * Copyright (C) 2020, 2022, D. R. Commander.
   * For conditions of distribution and use, see the accompanying README.ijg
   * file.
   *
   * This file contains initialization logic for the JPEG compressor.
   * This routine is in charge of selecting the modules to be executed and
   * making an initialization call to each one.
   *
   * Logically, this code belongs in jcmaster.c.  It's split out because
   * linking this routine implies linking the entire compression library.
   * For a transcoding-only application, we want to be able to use jcmaster.c
   * without linking in the whole library.
   */
  
  #define JPEG_INTERNALS
  #include "jinclude.h"
  #include "jpeglib.h"
  #include "jpegapicomp.h"
  
  
  /*
   * Master selection of compression modules.
   * This is done once at the start of processing an image.  We determine
   * which modules will be used and give them appropriate initialization calls.
   */
  
  GLOBAL(void)
  jinit_compress_master(j_compress_ptr cinfo)
  {
    /* Initialize master control (includes parameter checking/processing) */
    jinit_c_master_control(cinfo, FALSE /* full compression */);
  
    /* Preprocessing */
    if (!cinfo->raw_data_in) {
      if (cinfo->data_precision == 12) {
        j12init_color_converter(cinfo);
        j12init_downsampler(cinfo);
        j12init_c_prep_controller(cinfo,
                                  FALSE /* never need full buffer here */);
      } else {
        jinit_color_converter(cinfo);
        jinit_downsampler(cinfo);
        jinit_c_prep_controller(cinfo, FALSE /* never need full buffer here */);
      }
    }
  
    if (cinfo->master->lossless) {
  #ifdef C_LOSSLESS_SUPPORTED
      /* Prediction, sample differencing, and point transform */
      if (cinfo->data_precision == 12)
        j12init_lossless_compressor(cinfo);
      else
        jinit_lossless_compressor(cinfo);
      /* Entropy encoding: either Huffman or arithmetic coding. */
      if (cinfo->arith_code) {
        ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
      } else {
        jinit_lhuff_encoder(cinfo);
      }
  
      /* Need a full-image difference buffer in any multi-pass mode. */
      if (cinfo->data_precision == 12)
        j12init_c_diff_controller(cinfo, (boolean)(cinfo->num_scans > 1 ||
                                                   cinfo->optimize_coding));
      else
        jinit_c_diff_controller(cinfo, (boolean)(cinfo->num_scans > 1 ||
                                                 cinfo->optimize_coding));
  #else
      ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif
    } else {
      /* Forward DCT */
      if (cinfo->data_precision == 12)
        j12init_forward_dct(cinfo);
      else
        jinit_forward_dct(cinfo);
      /* Entropy encoding: either Huffman or arithmetic coding. */
      if (cinfo->arith_code) {
  #ifdef C_ARITH_CODING_SUPPORTED
        jinit_arith_encoder(cinfo);
  #else
        ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
  #endif
      } else {
        if (cinfo->progressive_mode) {
  #ifdef C_PROGRESSIVE_SUPPORTED
          jinit_phuff_encoder(cinfo);
  #else
          ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif
        } else
          jinit_huff_encoder(cinfo);
      }
  
      /* Need a full-image coefficient buffer in any multi-pass mode. */
      if (cinfo->data_precision == 12)
        j12init_c_coef_controller(cinfo, (boolean)(cinfo->num_scans > 1 ||
                                                   cinfo->optimize_coding));
      else
        jinit_c_coef_controller(cinfo, (boolean)(cinfo->num_scans > 1 ||
                                                 cinfo->optimize_coding));
    }
  
    if (cinfo->data_precision == 12)
      j12init_c_main_controller(cinfo, FALSE /* never need full buffer here */);
    else
      jinit_c_main_controller(cinfo, FALSE /* never need full buffer here */);
  
    jinit_marker_writer(cinfo);
  
    /* We can now tell the memory manager to allocate virtual arrays. */
    (*cinfo->mem->realize_virt_arrays) ((j_common_ptr)cinfo);
  
    /* Write the datastream header (SOI) immediately.
     * Frame and scan headers are postponed till later.
     * This lets application insert special markers after the SOI.
     */
    (*cinfo->marker->write_file_header) (cinfo);
  }
  

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