cdjpeg.h

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Hash : e8b40f3c
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Date : 2022-11-01T21:45:39

Vastly improve 12-bit JPEG integration

The Gordian knot that 7fec5074f962b20ed00b4f5da4533e1e8d4ed8ac attempted
to unravel was caused by the fact that there are several
data-precision-dependent (JSAMPLE-dependent) fields and methods in the
exposed libjpeg API structures, and if you change the exposed libjpeg
API structures, then you have to change the whole API.  If you change
the whole API, then you have to provide a whole new library to support
the new API, and that makes it difficult to support multiple data
precisions in the same application.  (It is not impossible, as example.c
demonstrated, but using data-precision-dependent libjpeg API structures
would have made the cjpeg, djpeg, and jpegtran source code hard to read,
so it made more sense to build, install, and package 12-bit-specific
versions of those applications.)

Unfortunately, the result of that initial integration effort was an
unreadable and unmaintainable mess, which is a problem for a library
that is an ISO/ITU-T reference implementation.  Also, as I dug into the
problem of lossless JPEG support, I realized that 16-bit lossless JPEG
images are a thing, and supporting yet another version of the libjpeg
API just for those images is untenable.

In fact, however, the touch points for JSAMPLE in the exposed libjpeg
API structures are minimal:

  - The colormap and sample_range_limit fields in jpeg_decompress_struct
  - The alloc_sarray() and access_virt_sarray() methods in
    jpeg_memory_mgr
  - jpeg_write_scanlines() and jpeg_write_raw_data()
  - jpeg_read_scanlines() and jpeg_read_raw_data()
  - jpeg_skip_scanlines() and jpeg_crop_scanline()
    (This is subtle, but both of those functions use JSAMPLE-dependent
    opaque structures behind the scenes.)

It is much more readable and maintainable to provide 12-bit-specific
versions of those six top-level API functions and to document that the
aforementioned methods and fields must be type-cast when using 12-bit
samples.  Since that eliminates the need to provide a 12-bit-specific
version of the exposed libjpeg API structures, we can:

  - Compile only the precision-dependent libjpeg modules (the
    coefficient buffer controllers, the colorspace converters, the
    DCT/IDCT managers, the main buffer controllers, the preprocessing
    and postprocessing controller, the downsampler and upsamplers, the
    quantizers, the integer DCT methods, and the IDCT methods) for
    multiple data precisions.
  - Introduce 12-bit-specific methods into the various internal
    structures defined in jpegint.h.
  - Create precision-independent data type, macro, method, field, and
    function names that are prefixed by an underscore, and use an
    internal header to convert those into precision-dependent data
    type, macro, method, field, and function names, based on the value
    of BITS_IN_JSAMPLE, when compiling the precision-dependent libjpeg
    modules.
  - Expose precision-dependent jinit*() functions for each of the
    precision-dependent libjpeg modules.
  - Abstract the precision-dependent libjpeg modules by calling the
    appropriate precision-dependent jinit*() function, based on the
    value of cinfo->data_precision, from top-level libjpeg API
    functions.

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cdjpeg.h

/*
 * cdjpeg.h
 *
 * This file was part of the Independent JPEG Group's software:
 * Copyright (C) 1994-1997, Thomas G. Lane.
 * Modified 2019 by Guido Vollbeding.
 * libjpeg-turbo Modifications:
 * Copyright (C) 2017, 2019, 2021-2022, D. R. Commander.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This file contains common declarations for the sample applications
 * cjpeg and djpeg.  It is NOT used by the core JPEG library.
 */

#define JPEG_CJPEG_DJPEG        /* define proper options in jconfig.h */
#define JPEG_INTERNAL_OPTIONS   /* cjpeg.c,djpeg.c need to see xxx_SUPPORTED */
#include "jinclude.h"
#include "jpeglib.h"
#include "jerror.h"             /* get library error codes too */
#include "cderror.h"            /* get application-specific error codes */


/*
 * Object interface for cjpeg's source file decoding modules
 */

typedef struct cjpeg_source_struct *cjpeg_source_ptr;

struct cjpeg_source_struct {
  void (*start_input) (j_compress_ptr cinfo, cjpeg_source_ptr sinfo);
  JDIMENSION (*get_pixel_rows) (j_compress_ptr cinfo, cjpeg_source_ptr sinfo);
  void (*finish_input) (j_compress_ptr cinfo, cjpeg_source_ptr sinfo);

  FILE *input_file;

  JSAMPARRAY buffer;
#ifdef WITH_12BIT
  J12SAMPARRAY buffer12;
#endif
  JDIMENSION buffer_height;
#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
  JDIMENSION max_pixels;
#endif
};


/*
 * Object interface for djpeg's output file encoding modules
 */

typedef struct djpeg_dest_struct *djpeg_dest_ptr;

struct djpeg_dest_struct {
  /* start_output is called after jpeg_start_decompress finishes.
   * The color map will be ready at this time, if one is needed.
   */
  void (*start_output) (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo);
  /* Emit the specified number of pixel rows from the buffer. */
  void (*put_pixel_rows) (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo,
                          JDIMENSION rows_supplied);
  /* Finish up at the end of the image. */
  void (*finish_output) (j_decompress_ptr cinfo, djpeg_dest_ptr dinfo);
  /* Re-calculate buffer dimensions based on output dimensions (for use with
     partial image decompression.)  If this is NULL, then the output format
     does not support partial image decompression (BMP, in particular, cannot
     support partial decompression because it uses an inversion buffer to write
     the image in bottom-up order.) */
  void (*calc_buffer_dimensions) (j_decompress_ptr cinfo,
                                  djpeg_dest_ptr dinfo);


  /* Target file spec; filled in by djpeg.c after object is created. */
  FILE *output_file;

  /* Output pixel-row buffer.  Created by module init or start_output.
   * Width is cinfo->output_width * cinfo->output_components;
   * height is buffer_height.
   */
  JSAMPARRAY buffer;
#ifdef WITH_12BIT
  J12SAMPARRAY buffer12;
#endif
  JDIMENSION buffer_height;
};


/*
 * cjpeg/djpeg may need to perform extra passes to convert to or from
 * the source/destination file format.  The JPEG library does not know
 * about these passes, but we'd like them to be counted by the progress
 * monitor.  We use an expanded progress monitor object to hold the
 * additional pass count.
 */

struct cdjpeg_progress_mgr {
  struct jpeg_progress_mgr pub; /* fields known to JPEG library */
  int completed_extra_passes;   /* extra passes completed */
  int total_extra_passes;       /* total extra */
  JDIMENSION max_scans;         /* abort if the number of scans exceeds this
                                   value and the value is non-zero */
  boolean report;               /* whether or not to report progress */
  /* last printed percentage stored here to avoid multiple printouts */
  int percent_done;
};

typedef struct cdjpeg_progress_mgr *cd_progress_ptr;


/* Module selection routines for I/O modules. */

EXTERN(cjpeg_source_ptr) jinit_read_bmp(j_compress_ptr cinfo,
                                        boolean use_inversion_array);
EXTERN(djpeg_dest_ptr) jinit_write_bmp(j_decompress_ptr cinfo, boolean is_os2,
                                       boolean use_inversion_array);
EXTERN(cjpeg_source_ptr) jinit_read_gif(j_compress_ptr cinfo);
EXTERN(djpeg_dest_ptr) jinit_write_gif(j_decompress_ptr cinfo, boolean is_lzw);
#ifdef WITH_12BIT
EXTERN(cjpeg_source_ptr) j12init_read_gif(j_compress_ptr cinfo);
EXTERN(djpeg_dest_ptr) j12init_write_gif(j_decompress_ptr cinfo,
                                         boolean is_lzw);
#endif
EXTERN(cjpeg_source_ptr) jinit_read_ppm(j_compress_ptr cinfo);
EXTERN(djpeg_dest_ptr) jinit_write_ppm(j_decompress_ptr cinfo);
#ifdef WITH_12BIT
EXTERN(cjpeg_source_ptr) j12init_read_ppm(j_compress_ptr cinfo);
EXTERN(djpeg_dest_ptr) j12init_write_ppm(j_decompress_ptr cinfo);
#endif
EXTERN(cjpeg_source_ptr) jinit_read_targa(j_compress_ptr cinfo);
EXTERN(djpeg_dest_ptr) jinit_write_targa(j_decompress_ptr cinfo);

/* cjpeg support routines (in rdswitch.c) */

EXTERN(boolean) read_quant_tables(j_compress_ptr cinfo, char *filename,
                                  boolean force_baseline);
EXTERN(boolean) read_scan_script(j_compress_ptr cinfo, char *filename);
EXTERN(boolean) set_quality_ratings(j_compress_ptr cinfo, char *arg,
                                    boolean force_baseline);
EXTERN(boolean) set_quant_slots(j_compress_ptr cinfo, char *arg);
EXTERN(boolean) set_sample_factors(j_compress_ptr cinfo, char *arg);

/* djpeg support routines (in rdcolmap.c) */

EXTERN(void) read_color_map(j_decompress_ptr cinfo, FILE *infile);
#ifdef WITH_12BIT
EXTERN(void) read_color_map_12(j_decompress_ptr cinfo, FILE *infile);
#endif

/* common support routines (in cdjpeg.c) */

EXTERN(void) start_progress_monitor(j_common_ptr cinfo,
                                    cd_progress_ptr progress);
EXTERN(void) end_progress_monitor(j_common_ptr cinfo);
EXTERN(boolean) keymatch(char *arg, const char *keyword, int minchars);
EXTERN(FILE *) read_stdin(void);
EXTERN(FILE *) write_stdout(void);

/* miscellaneous useful macros */

#ifdef DONT_USE_B_MODE          /* define mode parameters for fopen() */
#define READ_BINARY     "r"
#define WRITE_BINARY    "w"
#else
#define READ_BINARY     "rb"
#define WRITE_BINARY    "wb"
#endif

#ifndef EXIT_FAILURE            /* define exit() codes if not provided */
#define EXIT_FAILURE  1
#endif
#ifndef EXIT_SUCCESS
#define EXIT_SUCCESS  0
#endif
#ifndef EXIT_WARNING
#define EXIT_WARNING  2
#endif

#define IsExtRGB(cs) \
  (cs == JCS_RGB || (cs >= JCS_EXT_RGB && cs <= JCS_EXT_ARGB))

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kc3-lang/libjpeg-turbo/cdjpeg.h

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cdjpeg.h