ryan/mozjpeg
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Clean up the lossless JPEG feature

Browse Source 
- 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.
This commit is contained in:
DRC
2022-11-08 15:01:18 -06:00
parent ec6e451d05
commit 217d1a75f5
67 changed files with 3171 additions and 3871 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
cjpeg.c
View File

@@ -5,6 +5,7 @@
* Copyright (C) 1991-1998, Thomas G. Lane.
* Lossless JPEG Modifications:
* Copyright (C) 1999, Ken Murchison.
* Copyright (C) 2022, D. R. Commander.
* For conditions of distribution and use, see the accompanying README file.
*
* This file contains a command-line user interface for the JPEG compressor.
@@ -159,13 +160,13 @@ usage (void)
#ifdef C_PROGRESSIVE_SUPPORTED
fprintf(stderr, " -progressive Create progressive JPEG file\n");
#endif
#ifdef C_LOSSLESS_SUPPORTED
fprintf(stderr, " -lossless psv[,Pt] Create lossless JPEG file\n");
#endif
#ifdef TARGA_SUPPORTED
fprintf(stderr, " -targa Input file is Targa format (usually not needed)\n");
#endif
fprintf(stderr, "Switches for advanced users:\n");
#ifdef C_LOSSLESS_SUPPORTED
fprintf(stderr, " -lossless psv[,Pt] Create lossless JPEG file\n");
#endif
#ifdef DCT_ISLOW_SUPPORTED
fprintf(stderr, " -dct int Use integer DCT method%s\n",
(JDCT_DEFAULT == JDCT_ISLOW ? " (default)" : ""));
@@ -214,6 +215,9 @@ parse_switches (j_compress_ptr cinfo, int argc, char **argv,
{
int argn;
char * arg;
#ifdef C_LOSSLESS_SUPPORTED
int psv, pt = 0;
#endif
int quality; /* -quality parameter */
int q_scale_factor; /* scaling percentage for -qtables */
boolean force_baseline;
@@ -222,7 +226,6 @@ parse_switches (j_compress_ptr cinfo, int argc, char **argv,
char * qslotsarg = NULL; /* saves -qslots parm if any */
char * samplearg = NULL; /* saves -sample parm if any */
char * scansarg = NULL; /* saves -scans parm if any */
char * losslsarg = NULL; /* saves -lossless parm if any */
/* Set up default JPEG parameters. */
/* Note that default -quality level need not, and does not,
@@ -294,12 +297,20 @@ parse_switches (j_compress_ptr cinfo, int argc, char **argv,
jpeg_set_colorspace(cinfo, JCS_GRAYSCALE);
} else if (keymatch(arg, "lossless", 1)) {
/* Select simple lossless mode. */
/* Enable lossless mode. */
#ifdef C_LOSSLESS_SUPPORTED
char ch = ',', *ptr;
if (++argn >= argc) /* advance to next argument */
usage();
losslsarg = argv[argn];
/* We must postpone execution until num_components is known. */
if (sscanf(argv[argn], "%d%c", &psv, &ch) < 1 || ch != ',')
usage();
ptr = argv[argn];
while (*ptr && *ptr++ != ',') /* advance to next segment of arg string */
;
if (*ptr)
sscanf(ptr, "%d", &pt);
jpeg_enable_lossless(cinfo, psv, pt);
#else
fprintf(stderr, "%s: sorry, lossless output was not compiled\n",
progname);
@@ -461,12 +472,6 @@ parse_switches (j_compress_ptr cinfo, int argc, char **argv,
jpeg_simple_progression(cinfo);
#endif
#ifdef C_LOSSLESS_SUPPORTED
if (losslsarg != NULL) /* process -lossless if it was present */
if (! set_simple_lossless(cinfo, losslsarg))
usage();
#endif
#ifdef C_MULTISCAN_FILES_SUPPORTED
if (scansarg != NULL) /* process -scans if it was present */
if (! read_scan_script(cinfo, scansarg))