view release on metacpan or  search on metacpan

src/Source/LibJPEG/jmorecfg.h  view on Meta::CPAN

/*
 * jmorecfg.h
 *
 * Copyright (C) 1991-1997, Thomas G. Lane.
 * Modified 1997-2013 by Guido Vollbeding.
 * 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 additional configuration options that customize the
 * JPEG software for special applications or support machine-dependent
 * optimizations.  Most users will not need to touch this file.
 */


/*
 * Define BITS_IN_JSAMPLE as either
 *   8   for 8-bit sample values (the usual setting)
 *   9   for 9-bit sample values
 *   10  for 10-bit sample values
 *   11  for 11-bit sample values
 *   12  for 12-bit sample values
 * Only 8, 9, 10, 11, and 12 bits sample data precision are supported for
 * full-feature DCT processing.  Further depths up to 16-bit may be added
 * later for the lossless modes of operation.
 * Run-time selection and conversion of data precision will be added later
 * and are currently not supported, sorry.
 * Exception:  The transcoding part (jpegtran) supports all settings in a
 * single instance, since it operates on the level of DCT coefficients and
 * not sample values.  The DCT coefficients are of the same type (16 bits)
 * in all cases (see below).
 */

#define BITS_IN_JSAMPLE  8	/* use 8, 9, 10, 11, or 12 */


/*
 * Maximum number of components (color channels) allowed in JPEG image.
 * To meet the letter of the JPEG spec, set this to 255.  However, darn
 * few applications need more than 4 channels (maybe 5 for CMYK + alpha
 * mask).  We recommend 10 as a reasonable compromise; use 4 if you are
 * really short on memory.  (Each allowed component costs a hundred or so
 * bytes of storage, whether actually used in an image or not.)
 */

#define MAX_COMPONENTS  10	/* maximum number of image components */


/*
 * Basic data types.
 * You may need to change these if you have a machine with unusual data
 * type sizes; for example, "char" not 8 bits, "short" not 16 bits,
 * or "long" not 32 bits.  We don't care whether "int" is 16 or 32 bits,
 * but it had better be at least 16.
 */

/* Representation of a single sample (pixel element value).
 * We frequently allocate large arrays of these, so it's important to keep
 * them small.  But if you have memory to burn and access to char or short
 * arrays is very slow on your hardware, you might want to change these.
 */

#if BITS_IN_JSAMPLE == 8
/* JSAMPLE should be the smallest type that will hold the values 0..255.
 * You can use a signed char by having GETJSAMPLE mask it with 0xFF.
 */

#ifdef HAVE_UNSIGNED_CHAR

typedef unsigned char JSAMPLE;
#define GETJSAMPLE(value)  ((int) (value))

#else /* not HAVE_UNSIGNED_CHAR */

typedef char JSAMPLE;
#ifdef CHAR_IS_UNSIGNED
#define GETJSAMPLE(value)  ((int) (value))
#else
#define GETJSAMPLE(value)  ((int) (value) & 0xFF)
#endif /* CHAR_IS_UNSIGNED */

#endif /* HAVE_UNSIGNED_CHAR */

#define MAXJSAMPLE	255
#define CENTERJSAMPLE	128