chromium/third_party/libjpeg_turbo/rdswitch.c

/*
 * rdswitch.c
 *
 * This file was part of the Independent JPEG Group's software:
 * Copyright (C) 1991-1996, Thomas G. Lane.
 * libjpeg-turbo Modifications:
 * Copyright (C) 2010, 2018, 2022, D. R. Commander.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This file contains routines to process some of cjpeg's more complicated
 * command-line switches.  Switches processed here are:
 *      -qtables file           Read quantization tables from text file
 *      -scans file             Read scan script from text file
 *      -quality N[,N,...]      Set quality ratings
 *      -qslots N[,N,...]       Set component quantization table selectors
 *      -sample HxV[,HxV,...]   Set component sampling factors
 */

#ifdef _MSC_VER
#define _CRT_SECURE_NO_DEPRECATE
#endif

#include "cdjpeg.h"             /* Common decls for cjpeg/djpeg applications */
#include <ctype.h>              /* to declare isdigit(), isspace() */


LOCAL(int)
text_getc(FILE *file)
/* Read next char, skipping over any comments (# to end of line) */
/* A comment/newline sequence is returned as a newline */
{ … }


LOCAL(boolean)
read_text_integer(FILE *file, long *result, int *termchar)
/* Read an unsigned decimal integer from a file, store it in result */
/* Reads one trailing character after the integer; returns it in termchar */
{ … }


#if JPEG_LIB_VERSION < 70
static int q_scale_factor[NUM_QUANT_TBLS] = …;
#endif

GLOBAL(boolean)
read_quant_tables(j_compress_ptr cinfo, char *filename, boolean force_baseline)
/* Read a set of quantization tables from the specified file.
 * The file is plain ASCII text: decimal numbers with whitespace between.
 * Comments preceded by '#' may be included in the file.
 * There may be one to NUM_QUANT_TBLS tables in the file, each of 64 values.
 * The tables are implicitly numbered 0,1,etc.
 * NOTE: does not affect the qslots mapping, which will default to selecting
 * table 0 for luminance (or primary) components, 1 for chrominance components.
 * You must use -qslots if you want a different component->table mapping.
 */
{ … }


#ifdef C_MULTISCAN_FILES_SUPPORTED

LOCAL(boolean)
read_scan_integer(FILE *file, long *result, int *termchar)
/* Variant of read_text_integer that always looks for a non-space termchar;
 * this simplifies parsing of punctuation in scan scripts.
 */
{ … }


GLOBAL(boolean)
read_scan_script(j_compress_ptr cinfo, char *filename)
/* Read a scan script from the specified text file.
 * Each entry in the file defines one scan to be emitted.
 * Entries are separated by semicolons ';'.
 * An entry contains one to four component indexes,
 * optionally followed by a colon ':' and four progressive-JPEG parameters.
 * The component indexes denote which component(s) are to be transmitted
 * in the current scan.  The first component has index 0.
 * Sequential JPEG is used if the progressive-JPEG parameters are omitted.
 * The file is free format text: any whitespace may appear between numbers
 * and the ':' and ';' punctuation marks.  Also, other punctuation (such
 * as commas or dashes) can be placed between numbers if desired.
 * Comments preceded by '#' may be included in the file.
 * Note: we do very little validity checking here;
 * jcmaster.c will validate the script parameters.
 */
{ … }

#endif /* C_MULTISCAN_FILES_SUPPORTED */


#if JPEG_LIB_VERSION < 70
/* These are the sample quantization tables given in Annex K (Clause K.1) of
 * Recommendation ITU-T T.81 (1992) | ISO/IEC 10918-1:1994.
 * The spec says that the values given produce "good" quality, and
 * when divided by 2, "very good" quality.
 */
static const unsigned int std_luminance_quant_tbl[DCTSIZE2] = …;
static const unsigned int std_chrominance_quant_tbl[DCTSIZE2] = …;


LOCAL(void)
jpeg_default_qtables(j_compress_ptr cinfo, boolean force_baseline)
{ … }
#endif


GLOBAL(boolean)
set_quality_ratings(j_compress_ptr cinfo, char *arg, boolean force_baseline)
/* Process a quality-ratings parameter string, of the form
 *     N[,N,...]
 * If there are more q-table slots than parameters, the last value is replicated.
 */
{ … }


GLOBAL(boolean)
set_quant_slots(j_compress_ptr cinfo, char *arg)
/* Process a quantization-table-selectors parameter string, of the form
 *     N[,N,...]
 * If there are more components than parameters, the last value is replicated.
 */
{ … }


GLOBAL(boolean)
set_sample_factors(j_compress_ptr cinfo, char *arg)
/* Process a sample-factors parameter string, of the form
 *     HxV[,HxV,...]
 * If there are more components than parameters, "1x1" is assumed for the rest.
 */
{ … }