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.

README

@@ -74,10 +74,10 @@ remarkably high compression levels are possible if you can tolerate a
 low-quality image.  For more details, see the references, or just experiment
 with various compression settings.
 
-This software implements JPEG baseline, extended-sequential, progressive
-and lossless compression processes.  Provision is made for supporting all
-variants of these processes, although some uncommon parameter settings aren't
-implemented yet. For legal reasons, we are not distributing code for the
+This software implements JPEG baseline, extended-sequential, progressive, and
+lossless compression processes.  Provision is made for supporting all variants
+of these processes, although some uncommon parameter settings aren't
+implemented yet.  For legal reasons, we are not distributing code for the
 arithmetic-coding variants of JPEG; see LEGAL ISSUES.  We have made no
 provision for supporting the hierarchical processes defined in the standard.
 

TODO

@@ -6,8 +6,3 @@ List of things to complete for lossless codec:
 
 * How to check BITS_PER_JSAMPLE for lossy mode (ie, 16-bit data)? -
   see jdinput.c.
-
-* Check comment blocks for errors/changes.
-
-* Review new filenames.  Try to avoid filename conflicts with possible JPEG-LS
-  codec.

cdjpeg.h

@@ -1,10 +1,8 @@
 /*
  * cdjpeg.h
  *
- * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1994-1997, Thomas G. Lane.
- * Lossless JPEG Modifications:
- * Copyright (C) 1999, Ken Murchison.
+ * This file is part of the Independent JPEG Group's software.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains common declarations for the sample applications
@@ -137,7 +135,6 @@ EXTERN(boolean) read_quant_tables JPP((j_compress_ptr cinfo, char * filename,
 EXTERN(boolean) read_scan_script JPP((j_compress_ptr cinfo, char * filename));
 EXTERN(boolean) set_quant_slots JPP((j_compress_ptr cinfo, char *arg));
 EXTERN(boolean) set_sample_factors JPP((j_compress_ptr cinfo, char *arg));
-EXTERN(boolean) set_simple_lossless JPP((j_compress_ptr cinfo, char *arg));
 
 /* djpeg support routines (in rdcolmap.c) */
 

cjpeg.1

@@ -1,4 +1,4 @@
-.TH CJPEG 1 "27 April 1999"
+.TH CJPEG 1 "11 November 2022"
 .SH NAME
 cjpeg \- compress an image file to a JPEG file
 .SH SYNOPSIS
@@ -62,13 +62,6 @@ decompression are unaffected by
 .B \-progressive
 Create progressive JPEG file (see below).
 .TP
-.BI \-lossless " psv[,Pt]"
-Create a lossless JPEG file using the specified predictor selection value (1-7)
-and optional point transform.
-.B Caution:
-lossless JPEG is not widely implemented, so many decoders will be
-unable to view a lossless JPEG file at all.
-.TP
 .B \-targa
 Input file is Targa format.  Targa files that contain an "identification"
 field will not be automatically recognized by
@@ -130,6 +123,43 @@ unable to view a progressive JPEG file at all.
 .PP
 Switches for advanced users:
 .TP
+.BI \-lossless " psv[,Pt]"
+Create a lossless JPEG file using the specified predictor selection value
+(1 through 7) and optional point transform (0 through
+.nh
+.I precision
+.hy
+- 1, where
+.nh
+.I precision
+.hy
+is the JPEG data precision in bits).  A point transform value of 0 (the
+default) is necessary in order to create a fully lossless JPEG file.  (A
+non-zero point transform value right-shifts the input samples by the specified
+number of bits, which is effectively a form of lossy color quantization.)
+.B Caution:
+lossless JPEG is not yet widely implemented, so many decoders will be unable to
+view a lossless JPEG file at all.  Note that the following features will be
+unavailable when compressing or decompressing a lossless JPEG file:
+.IP
+- Quality/quantization table selection
+.IP
+- Color conversion (the JPEG image will use the same color space as the input
+image)
+.IP
+- DCT/IDCT algorithm selection
+.IP
+- Smoothing
+.IP
+- Downsampling/upsampling
+.IP
+- IDCT scaling
+.IP
+- Transformations using
+.B jpegtran
+.IP
+Any switches used to enable or configure those features will be ignored.
+.TP
 .B \-dct int
 Use integer DCT method (default).
 .TP
@@ -145,8 +175,8 @@ machines, while the integer methods should give the same results everywhere.
 The fast integer method is much less accurate than the other two.
 .TP
 .BI \-restart " N"
-Emit a JPEG restart marker every N MCU rows, or every N MCU blocks if "B" is
-attached to the number.
+Emit a JPEG restart marker every N MCU rows, or every N MCU blocks (samples in
+lossless mode) if "B" is attached to the number.
 .B \-restart 0
 (the default) means no restart markers.
 .TP

cjpeg.c

@@ -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))

filelist.doc

@@ -1,9 +1,10 @@
 IJG JPEG LIBRARY:  FILE LIST
 
 This file was part of the Independent JPEG Group's software:
-Copyright (C) 1994-1997, Thomas G. Lane.
+Copyright (C) 1994-1998, 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.
 
 
@@ -31,7 +32,6 @@ jinclude.h	Central include file used by all IJG .c files to reference
 		system include files.
 jpegint.h	JPEG library's internal data structures.
 jlossls.h	JPEG library's lossless codec data structures.
-jlossy.h	JPEG library's lossy codec structures.
 jchuff.h	Private declarations for Huffman encoder modules.
 jdhuff.h	Private declarations for Huffman decoder modules.
 jdct.h		Private declarations for forward & reverse DCT subsystems.
@@ -68,40 +68,37 @@ Compression side of the library:
 jcinit.c	Initialization: determines which other modules to use.
 jcmaster.c	Master control: setup and inter-pass sequencing logic.
 jcmainct.c	Main buffer controller (preprocessor => JPEG compressor).
-jchuff.c	Codec-independent Huffman entropy encoding routines.
 jcprepct.c	Preprocessor buffer controller.
 jccolor.c	Color space conversion.
 jcsample.c	Downsampling.
+jchuff.c	Shared Huffman entropy encoding routines.
 jcmarker.c	JPEG marker writing.
 jdatadst.c	Data destination manager for stdio output.
 
 Lossy (DCT) codec:
 
-jlossy.c	Lossy compressor proper.
 jccoefct.c	Buffer controller for DCT coefficient buffer.
 jcdctmgr.c	DCT manager (DCT implementation selection & control).
 jfdctint.c	Forward DCT using slow-but-accurate integer method.
 jfdctfst.c	Forward DCT using faster, less accurate integer method.
 jfdctflt.c	Forward DCT using floating-point arithmetic.
-jcshuff.c	Huffman entropy coding for sequential JPEG.
+jchuff.c	Huffman entropy coding for sequential JPEG.
 jcphuff.c	Huffman entropy coding for progressive JPEG.
 
 Lossless (spatial) codec:
 
-jclossls.c	Lossless compressor proper.
 jcdiffct.c	Buffer controller for difference buffer.
-jcscale.c	Point transformation.
-jcpred.c	Sample predictor and differencer.
+jclossls.c	Prediction, sample differencing, and point transform
 jclhuff.c	Huffman entropy encoding for lossless JPEG.
 
 Decompression side of the library:
 
 jdmaster.c	Master control: determines which other modules to use.
 jdinput.c	Input controller: controls input processing modules.
 jdmainct.c	Main buffer controller (JPEG decompressor => postprocessor).
-jdhuff.c	Codec-independent Huffman entropy decoding routines.
 jdpostct.c	Postprocessor buffer controller.
 jdmarker.c	JPEG marker reading.
+jdhuff.c	Shared Huffman entropy decoding routines.
 jdsample.c	Upsampling.
 jdcolor.c	Color space conversion.
 jdmerge.c	Merged upsampling/color conversion (faster, lower quality).
@@ -112,9 +109,8 @@ jdatasrc.c	Data source manager for stdio input.
 
 Lossy (DCT) codec:
 
-jdlossy.c	Lossy decompressor proper.
 jdcoefct.c	Buffer controller for DCT coefficient buffer.
-jdshuff.c	Huffman entropy decoding for sequential JPEG.
+jdhuff.c	Huffman entropy decoding for sequential JPEG.
 jdphuff.c	Huffman entropy decoding for progressive JPEG.
 jddctmgr.c	IDCT manager (IDCT implementation selection & control).
 jidctint.c	Inverse DCT using slow-but-accurate integer method.
@@ -124,17 +120,15 @@ jidctred.c	Inverse DCTs with reduced-size outputs.
 
 Lossless (spatial) codec:
 
-jdlossls.c	Lossless decompressor proper.
-jddiffct.c	Buffer controller for difference buffers.
+jddiffct.c	Buffer controller for difference buffer.
+jdlossls.c	Prediction, sample undifferencing, point transform, and sample
+		scaling
 jdlhuff.c	Huffman entropy decoding for lossless JPEG.
-jdpred.c	Sample predictor and undifferencer.
-jdscale.c	Point transformation, sample size scaling.
 
 Support files for both compression and decompression:
 
 jerror.c	Standard error handling routines (application replaceable).
 jmemmgr.c	System-independent (more or less) memory management code.
-jcodec.c	Codec-independent utility routines.
 jutils.c	Miscellaneous utility routines.
 
 jmemmgr.c relies on a system-dependent memory management module.  The IJG

jcapimin.c

@@ -4,7 +4,7 @@
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1994-1998, 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 application interface code for the compression half
@@ -21,6 +21,7 @@
 #define JPEG_INTERNALS
 #include "jinclude.h"
 #include "jpeglib.h"
+#include "jcmaster.h"
 
 
 /*
@@ -79,6 +80,14 @@ jpeg_CreateCompress (j_compress_ptr cinfo, int version, size_t structsize)
 
   /* OK, I'm ready */
   cinfo->global_state = CSTATE_START;
+
+  /* The master struct is used to store extension parameters, so we allocate it
+   * here.
+   */
+  cinfo->master = (struct jpeg_comp_master *)
+      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
+				  SIZEOF(my_comp_master));
+  MEMZERO(cinfo->master, SIZEOF(my_comp_master));
 }
 
 
@@ -170,7 +179,7 @@ jpeg_finish_compress (j_compress_ptr cinfo)
       /* We bypass the main controller and invoke coef controller directly;
        * all work is being done from the coefficient buffer.
        */
-      if (! (*cinfo->codec->compress_data) (cinfo, (JSAMPIMAGE) NULL))
+      if (! (*cinfo->coef->compress_data) (cinfo, (JSAMPIMAGE) NULL))
 	ERREXIT(cinfo, JERR_CANT_SUSPEND);
     }
     (*cinfo->master->finish_pass) (cinfo);

jcapistd.c

@@ -4,7 +4,7 @@
  * 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.
+ * Copyright (C) 2022, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains application interface code for the compression half
@@ -124,6 +124,9 @@ jpeg_write_raw_data (j_compress_ptr cinfo, JSAMPIMAGE data,
 {
   JDIMENSION lines_per_iMCU_row;
 
+  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) {
@@ -147,12 +150,12 @@ jpeg_write_raw_data (j_compress_ptr cinfo, JSAMPIMAGE data,
     (*cinfo->master->pass_startup) (cinfo);
 
   /* Verify that at least one iMCU row has been passed. */
-  lines_per_iMCU_row = cinfo->max_v_samp_factor * cinfo->data_unit;
+  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->codec->compress_data) (cinfo, data)) {
+  if (! (*cinfo->coef->compress_data) (cinfo, data)) {
     /* If compressor did not consume the whole row, suspend processing. */
     return 0;
   }