1/*
2 * reserved comment block
3 * DO NOT REMOVE OR ALTER!
4 */
5/*
6 * jdct.h
7 *
8 * Copyright (C) 1994-1996, Thomas G. Lane.
9 * This file is part of the Independent JPEG Group's software.
10 * For conditions of distribution and use, see the accompanying README file.
11 *
12 * This include file contains common declarations for the forward and
13 * inverse DCT modules. These declarations are private to the DCT managers
14 * (jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms.
15 * The individual DCT algorithms are kept in separate files to ease
16 * machine-dependent tuning (e.g., assembly coding).
17 */
18
19
20/*
21 * A forward DCT routine is given a pointer to a work area of type DCTELEM[];
22 * the DCT is to be performed in-place in that buffer. Type DCTELEM is int
23 * for 8-bit samples, INT32 for 12-bit samples. (NOTE: Floating-point DCT
24 * implementations use an array of type FAST_FLOAT, instead.)
25 * The DCT inputs are expected to be signed (range +-CENTERJSAMPLE).
26 * The DCT outputs are returned scaled up by a factor of 8; they therefore
27 * have a range of +-8K for 8-bit data, +-128K for 12-bit data. This
28 * convention improves accuracy in integer implementations and saves some
29 * work in floating-point ones.
30 * Quantization of the output coefficients is done by jcdctmgr.c.
31 */
32
33#if BITS_IN_JSAMPLE == 8
34typedef int DCTELEM; /* 16 or 32 bits is fine */
35#else
36typedef INT32 DCTELEM; /* must have 32 bits */
37#endif
38
39typedef JMETHOD(void, forward_DCT_method_ptr, (DCTELEM * data));
40typedef JMETHOD(void, float_DCT_method_ptr, (FAST_FLOAT * data));
41
42
43/*
44 * An inverse DCT routine is given a pointer to the input JBLOCK and a pointer
45 * to an output sample array. The routine must dequantize the input data as
46 * well as perform the IDCT; for dequantization, it uses the multiplier table
47 * pointed to by compptr->dct_table. The output data is to be placed into the
48 * sample array starting at a specified column. (Any row offset needed will
49 * be applied to the array pointer before it is passed to the IDCT code.)
50 * Note that the number of samples emitted by the IDCT routine is
51 * DCT_scaled_size * DCT_scaled_size.
52 */
53
54/* typedef inverse_DCT_method_ptr is declared in jpegint.h */
55
56/*
57 * Each IDCT routine has its own ideas about the best dct_table element type.
58 */
59
60typedef MULTIPLIER ISLOW_MULT_TYPE; /* short or int, whichever is faster */
61#if BITS_IN_JSAMPLE == 8
62typedef MULTIPLIER IFAST_MULT_TYPE; /* 16 bits is OK, use short if faster */
63#define IFAST_SCALE_BITS 2 /* fractional bits in scale factors */
64#else
65typedef INT32 IFAST_MULT_TYPE; /* need 32 bits for scaled quantizers */
66#define IFAST_SCALE_BITS 13 /* fractional bits in scale factors */
67#endif
68typedef FAST_FLOAT FLOAT_MULT_TYPE; /* preferred floating type */
69
70
71/*
72 * Each IDCT routine is responsible for range-limiting its results and
73 * converting them to unsigned form (0..MAXJSAMPLE). The raw outputs could
74 * be quite far out of range if the input data is corrupt, so a bulletproof
75 * range-limiting step is required. We use a mask-and-table-lookup method
76 * to do the combined operations quickly. See the comments with
77 * prepare_range_limit_table (in jdmaster.c) for more info.
78 */
79
80#define IDCT_range_limit(cinfo) ((cinfo)->sample_range_limit + CENTERJSAMPLE)
81
82#define RANGE_MASK (MAXJSAMPLE * 4 + 3) /* 2 bits wider than legal samples */
83
84
85/* Short forms of external names for systems with brain-damaged linkers. */
86
87#ifdef NEED_SHORT_EXTERNAL_NAMES
88#define jpeg_fdct_islow jFDislow
89#define jpeg_fdct_ifast jFDifast
90#define jpeg_fdct_float jFDfloat
91#define jpeg_idct_islow jRDislow
92#define jpeg_idct_ifast jRDifast
93#define jpeg_idct_float jRDfloat
94#define jpeg_idct_4x4 jRD4x4
95#define jpeg_idct_2x2 jRD2x2
96#define jpeg_idct_1x1 jRD1x1
97#endif /* NEED_SHORT_EXTERNAL_NAMES */
98
99/* Extern declarations for the forward and inverse DCT routines. */
100
101EXTERN(void) jpeg_fdct_islow JPP((DCTELEM * data));
102EXTERN(void) jpeg_fdct_ifast JPP((DCTELEM * data));
103EXTERN(void) jpeg_fdct_float JPP((FAST_FLOAT * data));
104
105EXTERN(void) jpeg_idct_islow
106 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
107 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
108EXTERN(void) jpeg_idct_ifast
109 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
110 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
111EXTERN(void) jpeg_idct_float
112 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
113 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
114EXTERN(void) jpeg_idct_4x4
115 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
116 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
117EXTERN(void) jpeg_idct_2x2
118 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
119 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
120EXTERN(void) jpeg_idct_1x1
121 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
122 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
123
124
125/*
126 * Macros for handling fixed-point arithmetic; these are used by many
127 * but not all of the DCT/IDCT modules.
128 *
129 * All values are expected to be of type INT32.
130 * Fractional constants are scaled left by CONST_BITS bits.
131 * CONST_BITS is defined within each module using these macros,
132 * and may differ from one module to the next.
133 */
134
135#define ONE ((INT32) 1)
136#define CONST_SCALE (ONE << CONST_BITS)
137
138/* Convert a positive real constant to an integer scaled by CONST_SCALE.
139 * Caution: some C compilers fail to reduce "FIX(constant)" at compile time,
140 * thus causing a lot of useless floating-point operations at run time.
141 */
142
143#define FIX(x) ((INT32) ((x) * CONST_SCALE + 0.5))
144
145/* Descale and correctly round an INT32 value that's scaled by N bits.
146 * We assume RIGHT_SHIFT rounds towards minus infinity, so adding
147 * the fudge factor is correct for either sign of X.
148 */
149
150#define DESCALE(x,n) RIGHT_SHIFT((x) + (ONE << ((n)-1)), n)
151
152/* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
153 * This macro is used only when the two inputs will actually be no more than
154 * 16 bits wide, so that a 16x16->32 bit multiply can be used instead of a
155 * full 32x32 multiply. This provides a useful speedup on many machines.
156 * Unfortunately there is no way to specify a 16x16->32 multiply portably
157 * in C, but some C compilers will do the right thing if you provide the
158 * correct combination of casts.
159 */
160
161#ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */
162#define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT16) (const)))
163#endif
164#ifdef SHORTxLCONST_32 /* known to work with Microsoft C 6.0 */
165#define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT32) (const)))
166#endif
167
168#ifndef MULTIPLY16C16 /* default definition */
169#define MULTIPLY16C16(var,const) ((var) * (const))
170#endif
171
172/* Same except both inputs are variables. */
173
174#ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */
175#define MULTIPLY16V16(var1,var2) (((INT16) (var1)) * ((INT16) (var2)))
176#endif
177
178#ifndef MULTIPLY16V16 /* default definition */
179#define MULTIPLY16V16(var1,var2) ((var1) * (var2))
180#endif
181