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[d2df-sdl.git] / src / lib / vampimg / JpegLib / imjdct.pas
1 unit imjdct;
3 { Orignal: jdct.h; Copyright (C) 1994-1996, Thomas G. Lane. }
5 { This include file contains common declarations for the forward and
6 inverse DCT modules. These declarations are private to the DCT managers
7 (jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms.
8 The individual DCT algorithms are kept in separate files to ease
9 machine-dependent tuning (e.g., assembly coding). }
11 interface
13 {$I imjconfig.inc}
15 uses
16 imjmorecfg;
19 { A forward DCT routine is given a pointer to a work area of type DCTELEM[];
20 the DCT is to be performed in-place in that buffer. Type DCTELEM is int
21 for 8-bit samples, INT32 for 12-bit samples. (NOTE: Floating-point DCT
22 implementations use an array of type FAST_FLOAT, instead.)
23 The DCT inputs are expected to be signed (range +-CENTERJSAMPLE).
24 The DCT outputs are returned scaled up by a factor of 8; they therefore
25 have a range of +-8K for 8-bit data, +-128K for 12-bit data. This
26 convention improves accuracy in integer implementations and saves some
27 work in floating-point ones.
28 Quantization of the output coefficients is done by jcdctmgr.c. }
31 {$ifdef BITS_IN_JSAMPLE_IS_8}
32 type
33 DCTELEM = int; { 16 or 32 bits is fine }
34 {$else}
35 type { must have 32 bits }
36 DCTELEM = INT32;
37 {$endif}
38 type
39 jTDctElem = 0..(MaxInt div SizeOf(DCTELEM))-1;
40 DCTELEM_FIELD = array[jTDctElem] of DCTELEM;
41 DCTELEM_FIELD_PTR = ^DCTELEM_FIELD;
42 DCTELEMPTR = ^DCTELEM;
44 type
45 forward_DCT_method_ptr = procedure(var data : array of DCTELEM);
46 float_DCT_method_ptr = procedure(var data : array of FAST_FLOAT);
49 { An inverse DCT routine is given a pointer to the input JBLOCK and a pointer
50 to an output sample array. The routine must dequantize the input data as
51 well as perform the IDCT; for dequantization, it uses the multiplier table
52 pointed to by compptr->dct_table. The output data is to be placed into the
53 sample array starting at a specified column. (Any row offset needed will
54 be applied to the array pointer before it is passed to the IDCT code.)
55 Note that the number of samples emitted by the IDCT routine is
56 DCT_scaled_size * DCT_scaled_size. }
59 { typedef inverse_DCT_method_ptr is declared in jpegint.h }
62 { Each IDCT routine has its own ideas about the best dct_table element type. }
65 type
66 ISLOW_MULT_TYPE = MULTIPLIER; { short or int, whichever is faster }
68 {$ifdef BITS_IN_JSAMPLE_IS_8}
69 type
70 IFAST_MULT_TYPE = MULTIPLIER; { 16 bits is OK, use short if faster }
71 const
72 IFAST_SCALE_BITS = 2; { fractional bits in scale factors }
73 {$else}
74 type
75 IFAST_MULT_TYPE = INT32; { need 32 bits for scaled quantizers }
76 const
77 IFAST_SCALE_BITS = 13; { fractional bits in scale factors }
78 {$endif}
79 type
80 FLOAT_MULT_TYPE = FAST_FLOAT; { preferred floating type }
82 const
83 RANGE_MASK = (MAXJSAMPLE * 4 + 3); { 2 bits wider than legal samples }
85 type
86 jTMultType = 0..(MaxInt div SizeOf(ISLOW_MULT_TYPE))-1;
87 ISLOW_MULT_TYPE_FIELD = array[jTMultType] of ISLOW_MULT_TYPE;
88 ISLOW_MULT_TYPE_FIELD_PTR = ^ISLOW_MULT_TYPE_FIELD;
89 ISLOW_MULT_TYPE_PTR = ^ISLOW_MULT_TYPE;
91 jTFloatType = 0..(MaxInt div SizeOf(FLOAT_MULT_TYPE))-1;
92 FLOAT_MULT_TYPE_FIELD = array[jTFloatType] of FLOAT_MULT_TYPE;
93 FLOAT_MULT_TYPE_FIELD_PTR = ^FLOAT_MULT_TYPE_FIELD;
94 FLOAT_MULT_TYPE_PTR = ^FLOAT_MULT_TYPE;
96 jTFastType = 0..(MaxInt div SizeOf(IFAST_MULT_TYPE))-1;
97 IFAST_MULT_TYPE_FIELD = array[jTFastType] of IFAST_MULT_TYPE;
98 IFAST_MULT_TYPE_FIELD_PTR = ^IFAST_MULT_TYPE_FIELD;
99 IFAST_MULT_TYPE_PTR = ^IFAST_MULT_TYPE;
101 type
102 jTFastFloat = 0..(MaxInt div SizeOf(FAST_FLOAT))-1;
103 FAST_FLOAT_FIELD = array[jTFastFloat] of FAST_FLOAT;
104 FAST_FLOAT_FIELD_PTR = ^FAST_FLOAT_FIELD;
105 FAST_FLOAT_PTR = ^FAST_FLOAT;
107 implementation
109 end.