161 lines
6.9 KiB
C
161 lines
6.9 KiB
C
// * jdct.h
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// *
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// * Copyright (C) 1994, Thomas G. Lane.
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// * This file is part of the Independent JPEG Group's software.
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// * For conditions of distribution and use, see the accompanying README file.
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// *
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// * This include file contains common declarations for the forward and
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// * inverse DCT modules. These declarations are private to the DCT managers
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// * (jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms.
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// * The individual DCT algorithms are kept in separate files to ease
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// * machine-dependent tuning (e.g., assembly coding).
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// * A forward DCT routine is given a pointer to a work area of type DCTELEM[];
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// * the DCT is to be performed in-place in that buffer. Type DCTELEM is int
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// * for 8-bit samples, INT32 for 12-bit samples. (NOTE: Floating-point DCT
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// * implementations use an array of type FAST_FLOAT, instead.)
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// * The DCT inputs are expected to be signed (range +-CENTERJSAMPLE).
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// * The DCT outputs are returned scaled up by a factor of 8; they therefore
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// * have a range of +-8K for 8-bit data, +-128K for 12-bit data. This
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// * convention improves accuracy in integer implementations and saves some
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// * work in floating-point ones.
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// * Quantization of the output coefficients is done by jcdctmgr.c.
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#if BITS_IN_JSAMPLE == 8
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typedef int DCTELEM; // 16 or 32 bits is fine
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#else
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typedef INT32 DCTELEM; // must have 32 bits
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#endif
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typedef JMETHOD(void, forward_DCT_method_ptr, (DCTELEM * data));
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typedef JMETHOD(void, float_DCT_method_ptr, (FAST_FLOAT * data));
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// * An inverse DCT routine is given a pointer to the input JBLOCK and a pointer
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// * to an output sample array. The routine must dequantize the input data as
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// * well as perform the IDCT; for dequantization, it uses the multiplier table
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// * pointed to by compptr->dct_table. The output data is to be placed into the
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// * sample array starting at a specified column. (Any row offset needed will
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// * be applied to the array pointer before it is passed to the IDCT code.)
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// * Note that the number of samples emitted by the IDCT routine is
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// * DCT_scaled_size * DCT_scaled_size.
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// typedef inverse_DCT_method_ptr is declared in jpegint.h
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// * Each IDCT routine has its own ideas about the best dct_table element type.
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typedef MULTIPLIER ISLOW_MULT_TYPE; // short or int, whichever is faster
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#if BITS_IN_JSAMPLE == 8
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typedef MULTIPLIER IFAST_MULT_TYPE; // 16 bits is OK, use short if faster
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#define IFAST_SCALE_BITS 2 // fractional bits in scale factors
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#else
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typedef INT32 IFAST_MULT_TYPE; // need 32 bits for scaled quantizers
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#define IFAST_SCALE_BITS 13 // fractional bits in scale factors
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#endif
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typedef FAST_FLOAT FLOAT_MULT_TYPE; // preferred floating type
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// * Each IDCT routine is responsible for range-limiting its results and
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// * converting them to unsigned form (0..MAXJSAMPLE). The raw outputs could
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// * be quite far out of range if the input data is corrupt, so a bulletproof
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// * range-limiting step is required. We use a mask-and-table-lookup method
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// * to do the combined operations quickly. See the comments with
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// * prepare_range_limit_table (in jdmaster.c) for more info.
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#define IDCT_range_limit(cinfo) ((cinfo)->sample_range_limit + CENTERJSAMPLE)
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#define RANGE_MASK (MAXJSAMPLE * 4 + 3) // 2 bits wider than legal samples
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// Short forms of external names for systems with brain-damaged linkers.
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#ifdef NEED_SHORT_EXTERNAL_NAMES
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#define jpeg_fdct_islow jFDislow
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#define jpeg_fdct_ifast jFDifast
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#define jpeg_fdct_float jFDfloat
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#define jpeg_idct_islow jRDislow
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#define jpeg_idct_ifast jRDifast
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#define jpeg_idct_float jRDfloat
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#define jpeg_idct_4x4 jRD4x4
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#define jpeg_idct_2x2 jRD2x2
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#define jpeg_idct_1x1 jRD1x1
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#endif // NEED_SHORT_EXTERNAL_NAMES
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// Extern declarations for the forward and inverse DCT routines.
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EXTERN void jpeg_fdct_islow JPP((DCTELEM * data));
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EXTERN void jpeg_fdct_ifast JPP((DCTELEM * data));
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EXTERN void jpeg_fdct_float JPP((FAST_FLOAT * data));
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EXTERN void jpeg_idct_islow
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JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
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JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
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EXTERN void jpeg_idct_ifast
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JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
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JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
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EXTERN void jpeg_idct_float
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JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
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JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
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EXTERN void jpeg_idct_4x4
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JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
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JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
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EXTERN void jpeg_idct_2x2
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JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
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JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
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EXTERN void jpeg_idct_1x1
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JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
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JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
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// * Macros for handling fixed-point arithmetic; these are used by many
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// * but not all of the DCT/IDCT modules.
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// *
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// * All values are expected to be of type INT32.
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// * Fractional constants are scaled left by CONST_BITS bits.
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// * CONST_BITS is defined within each module using these macros,
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// * and may differ from one module to the next.
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#define ONE ((INT32) 1)
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#define CONST_SCALE (ONE << CONST_BITS)
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// Convert a positive real constant to an integer scaled by CONST_SCALE.
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// * Caution: some C compilers fail to reduce "FIX(constant)" at compile time,
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// * thus causing a lot of useless floating-point operations at run time.
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#define FIX(x) ((INT32) ((x) * CONST_SCALE + 0.5))
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// Descale and correctly round an INT32 value that's scaled by N bits.
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// * We assume RIGHT_SHIFT rounds towards minus infinity, so adding
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// * the fudge factor is correct for either sign of X.
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#define DESCALE(x,n) RIGHT_SHIFT((x) + (ONE << ((n)-1)), n)
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// Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
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// * This macro is used only when the two inputs will actually be no more than
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// * 16 bits wide, so that a 16x16->32 bit multiply can be used instead of a
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// * full 32x32 multiply. This provides a useful speedup on many machines.
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// * Unfortunately there is no way to specify a 16x16->32 multiply portably
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// * in C, but some C compilers will do the right thing if you provide the
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// * correct combination of casts.
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#ifdef SHORTxSHORT_32 // may work if 'int' is 32 bits
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#define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT16) (const)))
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#endif
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#ifdef SHORTxLCONST_32 // known to work with Microsoft C 6.0
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#define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT32) (const)))
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#endif
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#ifndef MULTIPLY16C16 // default definition
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#define MULTIPLY16C16(var,const) ((var) * (const))
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#endif
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// Same except both inputs are variables.
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#ifdef SHORTxSHORT_32 // may work if 'int' is 32 bits
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#define MULTIPLY16V16(var1,var2) (((INT16) (var1)) * ((INT16) (var2)))
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#endif
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#ifndef MULTIPLY16V16 // default definition
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#define MULTIPLY16V16(var1,var2) ((var1) * (var2))
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#endif
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