110 lines
3.8 KiB
Plaintext
110 lines
3.8 KiB
Plaintext
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unit imjdct;
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{ Orignal: jdct.h; Copyright (C) 1994-1996, Thomas G. Lane. }
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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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interface
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{$I imjconfig.inc}
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uses
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imjmorecfg;
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{ A forward DCT routine is given a pointer to a work area of type DCTELEM[];
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the DCT is to be performed in-place in that buffer. Type DCTELEM is int
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for 8-bit samples, INT32 for 12-bit samples. (NOTE: Floating-point DCT
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implementations use an array of type FAST_FLOAT, instead.)
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The DCT inputs are expected to be signed (range +-CENTERJSAMPLE).
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The DCT outputs are returned scaled up by a factor of 8; they therefore
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have a range of +-8K for 8-bit data, +-128K for 12-bit data. This
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convention improves accuracy in integer implementations and saves some
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work in floating-point ones.
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Quantization of the output coefficients is done by jcdctmgr.c. }
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{$ifdef BITS_IN_JSAMPLE_IS_8}
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type
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DCTELEM = int; { 16 or 32 bits is fine }
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{$else}
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type { must have 32 bits }
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DCTELEM = INT32;
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{$endif}
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type
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jTDctElem = 0..(MaxInt div SizeOf(DCTELEM))-1;
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DCTELEM_FIELD = array[jTDctElem] of DCTELEM;
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DCTELEM_FIELD_PTR = ^DCTELEM_FIELD;
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DCTELEMPTR = ^DCTELEM;
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type
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forward_DCT_method_ptr = procedure(var data : array of DCTELEM);
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float_DCT_method_ptr = procedure(var data : array of FAST_FLOAT);
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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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type
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ISLOW_MULT_TYPE = MULTIPLIER; { short or int, whichever is faster }
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{$ifdef BITS_IN_JSAMPLE_IS_8}
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type
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IFAST_MULT_TYPE = MULTIPLIER; { 16 bits is OK, use short if faster }
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const
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IFAST_SCALE_BITS = 2; { fractional bits in scale factors }
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{$else}
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type
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IFAST_MULT_TYPE = INT32; { need 32 bits for scaled quantizers }
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const
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IFAST_SCALE_BITS = 13; { fractional bits in scale factors }
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{$endif}
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type
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FLOAT_MULT_TYPE = FAST_FLOAT; { preferred floating type }
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const
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RANGE_MASK = (MAXJSAMPLE * 4 + 3); { 2 bits wider than legal samples }
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type
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jTMultType = 0..(MaxInt div SizeOf(ISLOW_MULT_TYPE))-1;
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ISLOW_MULT_TYPE_FIELD = array[jTMultType] of ISLOW_MULT_TYPE;
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ISLOW_MULT_TYPE_FIELD_PTR = ^ISLOW_MULT_TYPE_FIELD;
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ISLOW_MULT_TYPE_PTR = ^ISLOW_MULT_TYPE;
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jTFloatType = 0..(MaxInt div SizeOf(FLOAT_MULT_TYPE))-1;
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FLOAT_MULT_TYPE_FIELD = array[jTFloatType] of FLOAT_MULT_TYPE;
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FLOAT_MULT_TYPE_FIELD_PTR = ^FLOAT_MULT_TYPE_FIELD;
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FLOAT_MULT_TYPE_PTR = ^FLOAT_MULT_TYPE;
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jTFastType = 0..(MaxInt div SizeOf(IFAST_MULT_TYPE))-1;
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IFAST_MULT_TYPE_FIELD = array[jTFastType] of IFAST_MULT_TYPE;
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IFAST_MULT_TYPE_FIELD_PTR = ^IFAST_MULT_TYPE_FIELD;
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IFAST_MULT_TYPE_PTR = ^IFAST_MULT_TYPE;
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type
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jTFastFloat = 0..(MaxInt div SizeOf(FAST_FLOAT))-1;
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FAST_FLOAT_FIELD = array[jTFastFloat] of FAST_FLOAT;
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FAST_FLOAT_FIELD_PTR = ^FAST_FLOAT_FIELD;
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FAST_FLOAT_PTR = ^FAST_FLOAT;
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implementation
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end.
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