2 * CDE - Common Desktop Environment
4 * Copyright (c) 1993-2012, The Open Group. All rights reserved.
6 * These libraries and programs are free software; you can
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8 * Lesser General Public License as published by the Free Software
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15 * PURPOSE. See the GNU Lesser General Public License for more
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with these librararies and programs; if not, write
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23 /* $XConsortium: jdct.h /main/2 1996/05/09 03:47:21 drk $ */
27 * Copyright (C) 1994-1996, Thomas G. Lane.
28 * This file is part of the Independent JPEG Group's software.
29 * For conditions of distribution and use, see the accompanying README file.
31 * This include file contains common declarations for the forward and
32 * inverse DCT modules. These declarations are private to the DCT managers
33 * (jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms.
34 * The individual DCT algorithms are kept in separate files to ease
35 * machine-dependent tuning (e.g., assembly coding).
40 * A forward DCT routine is given a pointer to a work area of type DCTELEM[];
41 * the DCT is to be performed in-place in that buffer. Type DCTELEM is int
42 * for 8-bit samples, INT32 for 12-bit samples. (NOTE: Floating-point DCT
43 * implementations use an array of type FAST_FLOAT, instead.)
44 * The DCT inputs are expected to be signed (range +-CENTERJSAMPLE).
45 * The DCT outputs are returned scaled up by a factor of 8; they therefore
46 * have a range of +-8K for 8-bit data, +-128K for 12-bit data. This
47 * convention improves accuracy in integer implementations and saves some
48 * work in floating-point ones.
49 * Quantization of the output coefficients is done by jcdctmgr.c.
52 #if BITS_IN_JSAMPLE == 8
53 typedef int DCTELEM; /* 16 or 32 bits is fine */
55 typedef INT32 DCTELEM; /* must have 32 bits */
58 typedef JMETHOD(void, forward_DCT_method_ptr, (DCTELEM * data));
59 typedef JMETHOD(void, float_DCT_method_ptr, (FAST_FLOAT * data));
63 * An inverse DCT routine is given a pointer to the input JBLOCK and a pointer
64 * to an output sample array. The routine must dequantize the input data as
65 * well as perform the IDCT; for dequantization, it uses the multiplier table
66 * pointed to by compptr->dct_table. The output data is to be placed into the
67 * sample array starting at a specified column. (Any row offset needed will
68 * be applied to the array pointer before it is passed to the IDCT code.)
69 * Note that the number of samples emitted by the IDCT routine is
70 * DCT_scaled_size * DCT_scaled_size.
73 /* typedef inverse_DCT_method_ptr is declared in jpegint.h */
76 * Each IDCT routine has its own ideas about the best dct_table element type.
79 typedef MULTIPLIER ISLOW_MULT_TYPE; /* short or int, whichever is faster */
80 #if BITS_IN_JSAMPLE == 8
81 typedef MULTIPLIER IFAST_MULT_TYPE; /* 16 bits is OK, use short if faster */
82 #define IFAST_SCALE_BITS 2 /* fractional bits in scale factors */
84 typedef INT32 IFAST_MULT_TYPE; /* need 32 bits for scaled quantizers */
85 #define IFAST_SCALE_BITS 13 /* fractional bits in scale factors */
87 typedef FAST_FLOAT FLOAT_MULT_TYPE; /* preferred floating type */
91 * Each IDCT routine is responsible for range-limiting its results and
92 * converting them to unsigned form (0..MAXJSAMPLE). The raw outputs could
93 * be quite far out of range if the input data is corrupt, so a bulletproof
94 * range-limiting step is required. We use a mask-and-table-lookup method
95 * to do the combined operations quickly. See the comments with
96 * prepare_range_limit_table (in jdmaster.c) for more info.
99 #define IDCT_range_limit(cinfo) ((cinfo)->sample_range_limit + CENTERJSAMPLE)
101 #define RANGE_MASK (MAXJSAMPLE * 4 + 3) /* 2 bits wider than legal samples */
104 /* Short forms of external names for systems with brain-damaged linkers. */
106 #ifdef NEED_SHORT_EXTERNAL_NAMES
107 #define jpeg_fdct_islow jFDislow
108 #define jpeg_fdct_ifast jFDifast
109 #define jpeg_fdct_float jFDfloat
110 #define jpeg_idct_islow jRDislow
111 #define jpeg_idct_ifast jRDifast
112 #define jpeg_idct_float jRDfloat
113 #define jpeg_idct_4x4 jRD4x4
114 #define jpeg_idct_2x2 jRD2x2
115 #define jpeg_idct_1x1 jRD1x1
116 #endif /* NEED_SHORT_EXTERNAL_NAMES */
118 /* Extern declarations for the forward and inverse DCT routines. */
120 EXTERN(void) jpeg_fdct_islow JPP((DCTELEM * data));
121 EXTERN(void) jpeg_fdct_ifast JPP((DCTELEM * data));
122 EXTERN(void) jpeg_fdct_float JPP((FAST_FLOAT * data));
124 EXTERN(void) jpeg_idct_islow
125 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
126 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
127 EXTERN(void) jpeg_idct_ifast
128 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
129 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
130 EXTERN(void) jpeg_idct_float
131 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
132 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
133 EXTERN(void) jpeg_idct_4x4
134 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
135 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
136 EXTERN(void) jpeg_idct_2x2
137 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
138 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
139 EXTERN(void) jpeg_idct_1x1
140 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
141 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
145 * Macros for handling fixed-point arithmetic; these are used by many
146 * but not all of the DCT/IDCT modules.
148 * All values are expected to be of type INT32.
149 * Fractional constants are scaled left by CONST_BITS bits.
150 * CONST_BITS is defined within each module using these macros,
151 * and may differ from one module to the next.
154 #define ONE ((INT32) 1)
155 #define CONST_SCALE (ONE << CONST_BITS)
157 /* Convert a positive real constant to an integer scaled by CONST_SCALE.
158 * Caution: some C compilers fail to reduce "FIX(constant)" at compile time,
159 * thus causing a lot of useless floating-point operations at run time.
162 #define FIX(x) ((INT32) ((x) * CONST_SCALE + 0.5))
164 /* Descale and correctly round an INT32 value that's scaled by N bits.
165 * We assume RIGHT_SHIFT rounds towards minus infinity, so adding
166 * the fudge factor is correct for either sign of X.
169 #define DESCALE(x,n) RIGHT_SHIFT((x) + (ONE << ((n)-1)), n)
171 /* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
172 * This macro is used only when the two inputs will actually be no more than
173 * 16 bits wide, so that a 16x16->32 bit multiply can be used instead of a
174 * full 32x32 multiply. This provides a useful speedup on many machines.
175 * Unfortunately there is no way to specify a 16x16->32 multiply portably
176 * in C, but some C compilers will do the right thing if you provide the
177 * correct combination of casts.
180 #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */
181 #define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT16) (const)))
183 #ifdef SHORTxLCONST_32 /* known to work with Microsoft C 6.0 */
184 #define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT32) (const)))
187 #ifndef MULTIPLY16C16 /* default definition */
188 #define MULTIPLY16C16(var,const) ((var) * (const))
191 /* Same except both inputs are variables. */
193 #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */
194 #define MULTIPLY16V16(var1,var2) (((INT16) (var1)) * ((INT16) (var2)))
197 #ifndef MULTIPLY16V16 /* default definition */
198 #define MULTIPLY16V16(var1,var2) ((var1) * (var2))