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

• /*
   * jdtrans.c
   *
   * This file was part of the Independent JPEG Group's software:
   * Copyright (C) 1995-1997, Thomas G. Lane.
   * 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 library routines for transcoding decompression,
   * that is, reading raw DCT coefficient arrays from an input JPEG file.
   * The routines in jdapimin.c will also be needed by a transcoder.
   */
  
  #define JPEG_INTERNALS
  #include "jinclude.h"
  #include "jpeglib.h"
  #include "jpegapicomp.h"
  
  
  /* Forward declarations */
  LOCAL(void) transdecode_master_selection(j_decompress_ptr cinfo);
  
  
  /*
   * Read the coefficient arrays from a JPEG file.
   * jpeg_read_header must be completed before calling this.
   *
   * The entire image is read into a set of virtual coefficient-block arrays,
   * one per component.  The return value is a pointer to the array of
   * virtual-array descriptors.  These can be manipulated directly via the
   * JPEG memory manager, or handed off to jpeg_write_coefficients().
   * To release the memory occupied by the virtual arrays, call
   * jpeg_finish_decompress() when done with the data.
   *
   * An alternative usage is to simply obtain access to the coefficient arrays
   * during a buffered-image-mode decompression operation.  This is allowed
   * after any jpeg_finish_output() call.  The arrays can be accessed until
   * jpeg_finish_decompress() is called.  (Note that any call to the library
   * may reposition the arrays, so don't rely on access_virt_barray() results
   * to stay valid across library calls.)
   *
   * Returns NULL if suspended.  This case need be checked only if
   * a suspending data source is used.
   */
  
  GLOBAL(jvirt_barray_ptr *)
  jpeg_read_coefficients(j_decompress_ptr cinfo)
  {
    if (cinfo->master->lossless)
      ERREXIT(cinfo, JERR_NOTIMPL);
  
    if (cinfo->global_state == DSTATE_READY) {
      /* First call: initialize active modules */
      transdecode_master_selection(cinfo);
      cinfo->global_state = DSTATE_RDCOEFS;
    }
    if (cinfo->global_state == DSTATE_RDCOEFS) {
      /* Absorb whole file into the coef buffer */
      for (;;) {
        int retcode;
        /* Call progress monitor hook if present */
        if (cinfo->progress != NULL)
          (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
        /* Absorb some more input */
        retcode = (*cinfo->inputctl->consume_input) (cinfo);
        if (retcode == JPEG_SUSPENDED)
          return NULL;
        if (retcode == JPEG_REACHED_EOI)
          break;
        /* Advance progress counter if appropriate */
        if (cinfo->progress != NULL &&
            (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
          if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
            /* startup underestimated number of scans; ratchet up one scan */
            cinfo->progress->pass_limit += (long)cinfo->total_iMCU_rows;
          }
        }
      }
      /* Set state so that jpeg_finish_decompress does the right thing */
      cinfo->global_state = DSTATE_STOPPING;
    }
    /* At this point we should be in state DSTATE_STOPPING if being used
     * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access
     * to the coefficients during a full buffered-image-mode decompression.
     */
    if ((cinfo->global_state == DSTATE_STOPPING ||
         cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) {
      return cinfo->coef->coef_arrays;
    }
    /* Oops, improper usage */
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
    return NULL;                  /* keep compiler happy */
  }
  
  
  /*
   * Master selection of decompression modules for transcoding.
   * This substitutes for jdmaster.c's initialization of the full decompressor.
   */
  
  LOCAL(void)
  transdecode_master_selection(j_decompress_ptr cinfo)
  {
    /* This is effectively a buffered-image operation. */
    cinfo->buffered_image = TRUE;
  
  #if JPEG_LIB_VERSION >= 80
    /* Compute output image dimensions and related values. */
    jpeg_core_output_dimensions(cinfo);
  #endif
  
    /* Entropy decoding: either Huffman or arithmetic coding. */
    if (cinfo->arith_code) {
  #ifdef D_ARITH_CODING_SUPPORTED
      jinit_arith_decoder(cinfo);
  #else
      ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
  #endif
    } else {
      if (cinfo->progressive_mode) {
  #ifdef D_PROGRESSIVE_SUPPORTED
        jinit_phuff_decoder(cinfo);
  #else
        ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif
      } else
        jinit_huff_decoder(cinfo);
    }
  
    /* Always get a full-image coefficient buffer. */
    if (cinfo->data_precision == 12)
      j12init_d_coef_controller(cinfo, TRUE);
    else
      jinit_d_coef_controller(cinfo, TRUE);
  
    /* We can now tell the memory manager to allocate virtual arrays. */
    (*cinfo->mem->realize_virt_arrays) ((j_common_ptr)cinfo);
  
    /* Initialize input side of decompressor to consume first scan. */
    (*cinfo->inputctl->start_input_pass) (cinfo);
  
    /* Initialize progress monitoring. */
    if (cinfo->progress != NULL) {
      int nscans;
      /* Estimate number of scans to set pass_limit. */
      if (cinfo->progressive_mode) {
        /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
        nscans = 2 + 3 * cinfo->num_components;
      } else if (cinfo->inputctl->has_multiple_scans) {
        /* For a nonprogressive multiscan file, estimate 1 scan per component. */
        nscans = cinfo->num_components;
      } else {
        nscans = 1;
      }
      cinfo->progress->pass_counter = 0L;
      cinfo->progress->pass_limit = (long)cinfo->total_iMCU_rows * nscans;
      cinfo->progress->completed_passes = 0;
      cinfo->progress->total_passes = 1;
    }
  }
  

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