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 * jdct.h
 *
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This include file contains common declarations for the forward and
 * inverse DCT modules.  These declarations are private to the DCT managers
 * (jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms.
 * The individual DCT algorithms are kept in separate files to ease 
 * machine-dependent tuning (e.g., assembly coding).
 */


/*
 * A forward DCT routine is given a pointer to an input sample array and
 * a pointer to a work area of type DCTELEM[]; the DCT is to be performed
 * in-place in that buffer.  Type DCTELEM is int for 8-bit samples, INT32
 * for 12-bit samples.  (NOTE: Floating-point DCT implementations use an
 * array of type FAST_FLOAT, instead.)
 * The input data is to be fetched from the sample array starting at a
 * specified column.  (Any row offset needed will be applied to the array
 * pointer before it is passed to the FDCT code.)
 * Note that the number of samples fetched by the FDCT routine is
 * DCT_h_scaled_size * DCT_v_scaled_size.
 * The DCT outputs are returned scaled up by a factor of 8; they therefore
 * have a range of +-8K for 8-bit data, +-128K for 12-bit data.  This
 * convention improves accuracy in integer implementations and saves some
 * work in floating-point ones.
 * Quantization of the output coefficients is done by jcdctmgr.c.
 */

#if BITS_IN_JSAMPLE == 8
typedef int DCTELEM;		/* 16 or 32 bits is fine */
#else
typedef INT32 DCTELEM;		/* must have 32 bits */
#endif

typedef JMETHOD(void, forward_DCT_method_ptr, (DCTELEM * data,
					       JSAMPARRAY sample_data,
					       JDIMENSION start_col));
typedef JMETHOD(void, float_DCT_method_ptr, (FAST_FLOAT * data,
					     JSAMPARRAY sample_data,
					     JDIMENSION start_col));


/*
 * An inverse DCT routine is given a pointer to the input JBLOCK and a pointer
 * to an output sample array.  The routine must dequantize the input data as
 * well as perform the IDCT; for dequantization, it uses the multiplier table
 * pointed to by compptr->dct_table.  The output data is to be placed into the
 * sample array starting at a specified column.  (Any row offset needed will
 * be applied to the array pointer before it is passed to the IDCT code.)
 * Note that the number of samples emitted by the IDCT routine is
 * DCT_h_scaled_size * DCT_v_scaled_size.
 */

/* typedef inverse_DCT_method_ptr is declared in jpegint.h */

/*
 * Each IDCT routine has its own ideas about the best dct_table element type.
 */

typedef MULTIPLIER ISLOW_MULT_TYPE; /* short or int, whichever is faster */
#if BITS_IN_JSAMPLE == 8
typedef MULTIPLIER IFAST_MULT_TYPE; /* 16 bits is OK, use short if faster */
#define IFAST_SCALE_BITS  2	/* fractional bits in scale factors */
#else
typedef INT32 IFAST_MULT_TYPE;	/* need 32 bits for scaled quantizers */
#define IFAST_SCALE_BITS  13	/* fractional bits in scale factors */
#endif
typedef FAST_FLOAT FLOAT_MULT_TYPE; /* preferred floating type */


/*
 * Each IDCT routine is responsible for range-limiting its results and
 * converting them to unsigned form (0..MAXJSAMPLE).  The raw outputs could
 * be quite far out of range if the input data is corrupt, so a bulletproof
 * range-limiting step is required.  We use a mask-and-table-lookup method
 * to do the combined operations quickly.  See the comments with
 * prepare_range_limit_table (in jdmaster.c) for more info.
 */

#define IDCT_range_limit(cinfo)  ((cinfo)->sample_range_limit + CENTERJSAMPLE)

#define RANGE_MASK  (MAXJSAMPLE * 4 + 3) /* 2 bits wider than legal samples */


/* Short forms of external names for systems with brain-damaged linkers. */

#ifdef NEED_SHORT_EXTERNAL_NAMES
#define jpeg_fdct_islow		jFDislow
#define jpeg_fdct_ifast		jFDifast
#define jpeg_fdct_float		jFDfloat
#define jpeg_fdct_7x7		jFD7x7
#define jpeg_fdct_6x6		jFD6x6
#define jpeg_fdct_5x5		jFD5x5
#define jpeg_fdct_4x4		jFD4x4
#define jpeg_fdct_3x3		jFD3x3
#define jpeg_fdct_2x2		jFD2x2
#define jpeg_fdct_1x1		jFD1x1
#define jpeg_fdct_9x9		jFD9x9
#define jpeg_fdct_10x10		jFD10x10
#define jpeg_fdct_11x11		jFD11x11
#define jpeg_fdct_12x12		jFD12x12
#define jpeg_fdct_13x13		jFD13x13
#define jpeg_fdct_14x14		jFD14x14
#define jpeg_fdct_15x15		jFD15x15
#define jpeg_fdct_16x16		jFD16x16
#define jpeg_fdct_16x8		jFD16x8
#define jpeg_fdct_14x7		jFD14x7
#define jpeg_fdct_12x6		jFD12x6
#define jpeg_fdct_10x5		jFD10x5
#define jpeg_fdct_8x4		jFD8x4
#define jpeg_fdct_6x3		jFD6x3
#define jpeg_fdct_4x2		jFD4x2
#define jpeg_fdct_2x1		jFD2x1
#define jpeg_fdct_8x16		jFD8x16
#define jpeg_fdct_7x14		jFD7x14
#define jpeg_fdct_6x12		jFD6x12
#define jpeg_fdct_5x10		jFD5x10