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

• /*
   * jcmainct.c
   *
   * This file was part of the Independent JPEG Group's software:
   * Copyright (C) 1994-1996, 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 file contains the main buffer controller for compression.
   * The main buffer lies between the pre-processor and the JPEG
   * compressor proper; it holds downsampled data in the JPEG colorspace.
   */
  
  #define JPEG_INTERNALS
  #include "jinclude.h"
  #include "jpeglib.h"
  #include "jsamplecomp.h"
  
  
  /* Private buffer controller object */
  
  typedef struct {
    struct jpeg_c_main_controller pub; /* public fields */
  
    JDIMENSION cur_iMCU_row;      /* number of current iMCU row */
    JDIMENSION rowgroup_ctr;      /* counts row groups received in iMCU row */
    boolean suspended;            /* remember if we suspended output */
    J_BUF_MODE pass_mode;         /* current operating mode */
  
    /* If using just a strip buffer, this points to the entire set of buffers
     * (we allocate one for each component).  In the full-image case, this
     * points to the currently accessible strips of the virtual arrays.
     */
    _JSAMPARRAY buffer[MAX_COMPONENTS];
  } my_main_controller;
  
  typedef my_main_controller *my_main_ptr;
  
  
  /* Forward declarations */
  METHODDEF(void) process_data_simple_main(j_compress_ptr cinfo,
                                           _JSAMPARRAY input_buf,
                                           JDIMENSION *in_row_ctr,
                                           JDIMENSION in_rows_avail);
  
  
  /*
   * Initialize for a processing pass.
   */
  
  METHODDEF(void)
  start_pass_main(j_compress_ptr cinfo, J_BUF_MODE pass_mode)
  {
    my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
  
    /* Do nothing in raw-data mode. */
    if (cinfo->raw_data_in)
      return;
  
    if (pass_mode != JBUF_PASS_THRU)
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
  
    main_ptr->cur_iMCU_row = 0;   /* initialize counters */
    main_ptr->rowgroup_ctr = 0;
    main_ptr->suspended = FALSE;
    main_ptr->pass_mode = pass_mode;      /* save mode for use by process_data */
    main_ptr->pub._process_data = process_data_simple_main;
  }
  
  
  /*
   * Process some data.
   * This routine handles the simple pass-through mode,
   * where we have only a strip buffer.
   */
  
  METHODDEF(void)
  process_data_simple_main(j_compress_ptr cinfo, _JSAMPARRAY input_buf,
                           JDIMENSION *in_row_ctr, JDIMENSION in_rows_avail)
  {
    my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
    JDIMENSION data_unit = cinfo->master->lossless ? 1 : DCTSIZE;
  
    while (main_ptr->cur_iMCU_row < cinfo->total_iMCU_rows) {
      /* Read input data if we haven't filled the main buffer yet */
      if (main_ptr->rowgroup_ctr < data_unit)
        (*cinfo->prep->_pre_process_data) (cinfo, input_buf, in_row_ctr,
                                           in_rows_avail, main_ptr->buffer,
                                           &main_ptr->rowgroup_ctr, data_unit);
  
      /* If we don't have a full iMCU row buffered, return to application for
       * more data.  Note that preprocessor will always pad to fill the iMCU row
       * at the bottom of the image.
       */
      if (main_ptr->rowgroup_ctr != data_unit)
        return;
  
      /* Send the completed row to the compressor */
      if (!(*cinfo->coef->_compress_data) (cinfo, main_ptr->buffer)) {
        /* If compressor did not consume the whole row, then we must need to
         * suspend processing and return to the application.  In this situation
         * we pretend we didn't yet consume the last input row; otherwise, if
         * it happened to be the last row of the image, the application would
         * think we were done.
         */
        if (!main_ptr->suspended) {
          (*in_row_ctr)--;
          main_ptr->suspended = TRUE;
        }
        return;
      }
      /* We did finish the row.  Undo our little suspension hack if a previous
       * call suspended; then mark the main buffer empty.
       */
      if (main_ptr->suspended) {
        (*in_row_ctr)++;
        main_ptr->suspended = FALSE;
      }
      main_ptr->rowgroup_ctr = 0;
      main_ptr->cur_iMCU_row++;
    }
  }
  
  
  /*
   * Initialize main buffer controller.
   */
  
  GLOBAL(void)
  _jinit_c_main_controller(j_compress_ptr cinfo, boolean need_full_buffer)
  {
    my_main_ptr main_ptr;
    int ci;
    jpeg_component_info *compptr;
    int data_unit = cinfo->master->lossless ? 1 : DCTSIZE;
  
    if (cinfo->data_precision != BITS_IN_JSAMPLE)
      ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
  
    main_ptr = (my_main_ptr)
      (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
                                  sizeof(my_main_controller));
    cinfo->main = (struct jpeg_c_main_controller *)main_ptr;
    main_ptr->pub.start_pass = start_pass_main;
  
    /* We don't need to create a buffer in raw-data mode. */
    if (cinfo->raw_data_in)
      return;
  
    /* Create the buffer.  It holds downsampled data, so each component
     * may be of a different size.
     */
    if (need_full_buffer) {
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    } else {
      /* Allocate a strip buffer for each component */
      for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
           ci++, compptr++) {
        main_ptr->buffer[ci] = (_JSAMPARRAY)(*cinfo->mem->alloc_sarray)
          ((j_common_ptr)cinfo, JPOOL_IMAGE,
           compptr->width_in_blocks * data_unit,
           (JDIMENSION)(compptr->v_samp_factor * data_unit));
      }
    }
  }
  

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