[LIBJPEG]
[reactos.git] / reactos / sdk / include / reactos / libs / libjpeg / jdct.h
1 /*
2 * jdct.h
3 *
4 * Copyright (C) 1994-1996, Thomas G. Lane.
5 * Modified 2002-2015 by Guido Vollbeding.
6 * This file is part of the Independent JPEG Group's software.
7 * For conditions of distribution and use, see the accompanying README file.
8 *
9 * This include file contains common declarations for the forward and
10 * inverse DCT modules. These declarations are private to the DCT managers
11 * (jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms.
12 * The individual DCT algorithms are kept in separate files to ease
13 * machine-dependent tuning (e.g., assembly coding).
14 */
15
16
17 /*
18 * A forward DCT routine is given a pointer to an input sample array and
19 * a pointer to a work area of type DCTELEM[]; the DCT is to be performed
20 * in-place in that buffer. Type DCTELEM is int for 8-bit samples, INT32
21 * for 12-bit samples. (NOTE: Floating-point DCT implementations use an
22 * array of type FAST_FLOAT, instead.)
23 * The input data is to be fetched from the sample array starting at a
24 * specified column. (Any row offset needed will be applied to the array
25 * pointer before it is passed to the FDCT code.)
26 * Note that the number of samples fetched by the FDCT routine is
27 * DCT_h_scaled_size * DCT_v_scaled_size.
28 * The DCT outputs are returned scaled up by a factor of 8; they therefore
29 * have a range of +-8K for 8-bit data, +-128K for 12-bit data. This
30 * convention improves accuracy in integer implementations and saves some
31 * work in floating-point ones.
32 * Quantization of the output coefficients is done by jcdctmgr.c.
33 */
34
35 #if BITS_IN_JSAMPLE == 8
36 typedef int DCTELEM; /* 16 or 32 bits is fine */
37 #else
38 typedef INT32 DCTELEM; /* must have 32 bits */
39 #endif
40
41 typedef JMETHOD(void, forward_DCT_method_ptr, (DCTELEM * data,
42 JSAMPARRAY sample_data,
43 JDIMENSION start_col));
44 typedef JMETHOD(void, float_DCT_method_ptr, (FAST_FLOAT * data,
45 JSAMPARRAY sample_data,
46 JDIMENSION start_col));
47
48
49 /*
50 * An inverse DCT routine is given a pointer to the input JBLOCK and a pointer
51 * to an output sample array. The routine must dequantize the input data as
52 * well as perform the IDCT; for dequantization, it uses the multiplier table
53 * pointed to by compptr->dct_table. The output data is to be placed into the
54 * sample array starting at a specified column. (Any row offset needed will
55 * be applied to the array pointer before it is passed to the IDCT code.)
56 * Note that the number of samples emitted by the IDCT routine is
57 * DCT_h_scaled_size * DCT_v_scaled_size.
58 */
59
60 /* typedef inverse_DCT_method_ptr is declared in jpegint.h */
61
62 /*
63 * Each IDCT routine has its own ideas about the best dct_table element type.
64 */
65
66 typedef MULTIPLIER ISLOW_MULT_TYPE; /* short or int, whichever is faster */
67 #if BITS_IN_JSAMPLE == 8
68 typedef MULTIPLIER IFAST_MULT_TYPE; /* 16 bits is OK, use short if faster */
69 #define IFAST_SCALE_BITS 2 /* fractional bits in scale factors */
70 #else
71 typedef INT32 IFAST_MULT_TYPE; /* need 32 bits for scaled quantizers */
72 #define IFAST_SCALE_BITS 13 /* fractional bits in scale factors */
73 #endif
74 typedef FAST_FLOAT FLOAT_MULT_TYPE; /* preferred floating type */
75
76
77 /*
78 * Each IDCT routine is responsible for range-limiting its results and
79 * converting them to unsigned form (0..MAXJSAMPLE). The raw outputs could
80 * be quite far out of range if the input data is corrupt, so a bulletproof
81 * range-limiting step is required. We use a mask-and-table-lookup method
82 * to do the combined operations quickly, assuming that MAXJSAMPLE+1
83 * is a power of 2. See the comments with prepare_range_limit_table
84 * (in jdmaster.c) for more info.
85 */
86
87 #define RANGE_MASK (MAXJSAMPLE * 4 + 3) /* 2 bits wider than legal samples */
88 #define RANGE_CENTER (MAXJSAMPLE * 2 + 2)
89 #define RANGE_SUBSET (RANGE_CENTER - CENTERJSAMPLE)
90
91 #define IDCT_range_limit(cinfo) ((cinfo)->sample_range_limit - RANGE_SUBSET)
92
93
94 /* Short forms of external names for systems with brain-damaged linkers. */
95
96 #ifdef NEED_SHORT_EXTERNAL_NAMES
97 #define jpeg_fdct_islow jFDislow
98 #define jpeg_fdct_ifast jFDifast
99 #define jpeg_fdct_float jFDfloat
100 #define jpeg_fdct_7x7 jFD7x7
101 #define jpeg_fdct_6x6 jFD6x6
102 #define jpeg_fdct_5x5 jFD5x5
103 #define jpeg_fdct_4x4 jFD4x4
104 #define jpeg_fdct_3x3 jFD3x3
105 #define jpeg_fdct_2x2 jFD2x2
106 #define jpeg_fdct_1x1 jFD1x1
107 #define jpeg_fdct_9x9 jFD9x9
108 #define jpeg_fdct_10x10 jFD10x10
109 #define jpeg_fdct_11x11 jFD11x11
110 #define jpeg_fdct_12x12 jFD12x12
111 #define jpeg_fdct_13x13 jFD13x13
112 #define jpeg_fdct_14x14 jFD14x14
113 #define jpeg_fdct_15x15 jFD15x15
114 #define jpeg_fdct_16x16 jFD16x16
115 #define jpeg_fdct_16x8 jFD16x8
116 #define jpeg_fdct_14x7 jFD14x7
117 #define jpeg_fdct_12x6 jFD12x6
118 #define jpeg_fdct_10x5 jFD10x5
119 #define jpeg_fdct_8x4 jFD8x4
120 #define jpeg_fdct_6x3 jFD6x3
121 #define jpeg_fdct_4x2 jFD4x2
122 #define jpeg_fdct_2x1 jFD2x1
123 #define jpeg_fdct_8x16 jFD8x16
124 #define jpeg_fdct_7x14 jFD7x14
125 #define jpeg_fdct_6x12 jFD6x12
126 #define jpeg_fdct_5x10 jFD5x10
127 #define jpeg_fdct_4x8 jFD4x8
128 #define jpeg_fdct_3x6 jFD3x6
129 #define jpeg_fdct_2x4 jFD2x4
130 #define jpeg_fdct_1x2 jFD1x2
131 #define jpeg_idct_islow jRDislow
132 #define jpeg_idct_ifast jRDifast
133 #define jpeg_idct_float jRDfloat
134 #define jpeg_idct_7x7 jRD7x7
135 #define jpeg_idct_6x6 jRD6x6
136 #define jpeg_idct_5x5 jRD5x5
137 #define jpeg_idct_4x4 jRD4x4
138 #define jpeg_idct_3x3 jRD3x3
139 #define jpeg_idct_2x2 jRD2x2
140 #define jpeg_idct_1x1 jRD1x1
141 #define jpeg_idct_9x9 jRD9x9
142 #define jpeg_idct_10x10 jRD10x10
143 #define jpeg_idct_11x11 jRD11x11
144 #define jpeg_idct_12x12 jRD12x12
145 #define jpeg_idct_13x13 jRD13x13
146 #define jpeg_idct_14x14 jRD14x14
147 #define jpeg_idct_15x15 jRD15x15
148 #define jpeg_idct_16x16 jRD16x16
149 #define jpeg_idct_16x8 jRD16x8
150 #define jpeg_idct_14x7 jRD14x7
151 #define jpeg_idct_12x6 jRD12x6
152 #define jpeg_idct_10x5 jRD10x5
153 #define jpeg_idct_8x4 jRD8x4
154 #define jpeg_idct_6x3 jRD6x3
155 #define jpeg_idct_4x2 jRD4x2
156 #define jpeg_idct_2x1 jRD2x1
157 #define jpeg_idct_8x16 jRD8x16
158 #define jpeg_idct_7x14 jRD7x14
159 #define jpeg_idct_6x12 jRD6x12
160 #define jpeg_idct_5x10 jRD5x10
161 #define jpeg_idct_4x8 jRD4x8
162 #define jpeg_idct_3x6 jRD3x8
163 #define jpeg_idct_2x4 jRD2x4
164 #define jpeg_idct_1x2 jRD1x2
165 #endif /* NEED_SHORT_EXTERNAL_NAMES */
166
167 /* Extern declarations for the forward and inverse DCT routines. */
168
169 EXTERN(void) jpeg_fdct_islow
170 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
171 EXTERN(void) jpeg_fdct_ifast
172 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
173 EXTERN(void) jpeg_fdct_float
174 JPP((FAST_FLOAT * data, JSAMPARRAY sample_data, JDIMENSION start_col));
175 EXTERN(void) jpeg_fdct_7x7
176 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
177 EXTERN(void) jpeg_fdct_6x6
178 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
179 EXTERN(void) jpeg_fdct_5x5
180 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
181 EXTERN(void) jpeg_fdct_4x4
182 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
183 EXTERN(void) jpeg_fdct_3x3
184 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
185 EXTERN(void) jpeg_fdct_2x2
186 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
187 EXTERN(void) jpeg_fdct_1x1
188 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
189 EXTERN(void) jpeg_fdct_9x9
190 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
191 EXTERN(void) jpeg_fdct_10x10
192 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
193 EXTERN(void) jpeg_fdct_11x11
194 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
195 EXTERN(void) jpeg_fdct_12x12
196 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
197 EXTERN(void) jpeg_fdct_13x13
198 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
199 EXTERN(void) jpeg_fdct_14x14
200 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
201 EXTERN(void) jpeg_fdct_15x15
202 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
203 EXTERN(void) jpeg_fdct_16x16
204 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
205 EXTERN(void) jpeg_fdct_16x8
206 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
207 EXTERN(void) jpeg_fdct_14x7
208 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
209 EXTERN(void) jpeg_fdct_12x6
210 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
211 EXTERN(void) jpeg_fdct_10x5
212 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
213 EXTERN(void) jpeg_fdct_8x4
214 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
215 EXTERN(void) jpeg_fdct_6x3
216 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
217 EXTERN(void) jpeg_fdct_4x2
218 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
219 EXTERN(void) jpeg_fdct_2x1
220 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
221 EXTERN(void) jpeg_fdct_8x16
222 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
223 EXTERN(void) jpeg_fdct_7x14
224 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
225 EXTERN(void) jpeg_fdct_6x12
226 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
227 EXTERN(void) jpeg_fdct_5x10
228 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
229 EXTERN(void) jpeg_fdct_4x8
230 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
231 EXTERN(void) jpeg_fdct_3x6
232 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
233 EXTERN(void) jpeg_fdct_2x4
234 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
235 EXTERN(void) jpeg_fdct_1x2
236 JPP((DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col));
237
238 EXTERN(void) jpeg_idct_islow
239 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
240 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
241 EXTERN(void) jpeg_idct_ifast
242 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
243 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
244 EXTERN(void) jpeg_idct_float
245 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
246 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
247 EXTERN(void) jpeg_idct_7x7
248 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
249 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
250 EXTERN(void) jpeg_idct_6x6
251 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
252 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
253 EXTERN(void) jpeg_idct_5x5
254 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
255 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
256 EXTERN(void) jpeg_idct_4x4
257 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
258 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
259 EXTERN(void) jpeg_idct_3x3
260 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
261 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
262 EXTERN(void) jpeg_idct_2x2
263 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
264 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
265 EXTERN(void) jpeg_idct_1x1
266 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
267 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
268 EXTERN(void) jpeg_idct_9x9
269 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
270 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
271 EXTERN(void) jpeg_idct_10x10
272 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
273 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
274 EXTERN(void) jpeg_idct_11x11
275 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
276 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
277 EXTERN(void) jpeg_idct_12x12
278 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
279 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
280 EXTERN(void) jpeg_idct_13x13
281 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
282 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
283 EXTERN(void) jpeg_idct_14x14
284 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
285 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
286 EXTERN(void) jpeg_idct_15x15
287 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
288 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
289 EXTERN(void) jpeg_idct_16x16
290 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
291 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
292 EXTERN(void) jpeg_idct_16x8
293 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
294 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
295 EXTERN(void) jpeg_idct_14x7
296 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
297 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
298 EXTERN(void) jpeg_idct_12x6
299 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
300 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
301 EXTERN(void) jpeg_idct_10x5
302 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
303 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
304 EXTERN(void) jpeg_idct_8x4
305 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
306 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
307 EXTERN(void) jpeg_idct_6x3
308 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
309 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
310 EXTERN(void) jpeg_idct_4x2
311 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
312 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
313 EXTERN(void) jpeg_idct_2x1
314 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
315 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
316 EXTERN(void) jpeg_idct_8x16
317 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
318 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
319 EXTERN(void) jpeg_idct_7x14
320 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
321 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
322 EXTERN(void) jpeg_idct_6x12
323 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
324 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
325 EXTERN(void) jpeg_idct_5x10
326 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
327 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
328 EXTERN(void) jpeg_idct_4x8
329 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
330 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
331 EXTERN(void) jpeg_idct_3x6
332 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
333 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
334 EXTERN(void) jpeg_idct_2x4
335 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
336 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
337 EXTERN(void) jpeg_idct_1x2
338 JPP((j_decompress_ptr cinfo, jpeg_component_info * compptr,
339 JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col));
340
341
342 /*
343 * Macros for handling fixed-point arithmetic; these are used by many
344 * but not all of the DCT/IDCT modules.
345 *
346 * All values are expected to be of type INT32.
347 * Fractional constants are scaled left by CONST_BITS bits.
348 * CONST_BITS is defined within each module using these macros,
349 * and may differ from one module to the next.
350 */
351
352 #define ONE ((INT32) 1)
353 #define CONST_SCALE (ONE << CONST_BITS)
354
355 /* Convert a positive real constant to an integer scaled by CONST_SCALE.
356 * Caution: some C compilers fail to reduce "FIX(constant)" at compile time,
357 * thus causing a lot of useless floating-point operations at run time.
358 */
359
360 #define FIX(x) ((INT32) ((x) * CONST_SCALE + 0.5))
361
362 /* Descale and correctly round an INT32 value that's scaled by N bits.
363 * We assume RIGHT_SHIFT rounds towards minus infinity, so adding
364 * the fudge factor is correct for either sign of X.
365 */
366
367 #define DESCALE(x,n) RIGHT_SHIFT((x) + (ONE << ((n)-1)), n)
368
369 /* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
370 * This macro is used only when the two inputs will actually be no more than
371 * 16 bits wide, so that a 16x16->32 bit multiply can be used instead of a
372 * full 32x32 multiply. This provides a useful speedup on many machines.
373 * Unfortunately there is no way to specify a 16x16->32 multiply portably
374 * in C, but some C compilers will do the right thing if you provide the
375 * correct combination of casts.
376 */
377
378 #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */
379 #define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT16) (const)))
380 #endif
381 #ifdef SHORTxLCONST_32 /* known to work with Microsoft C 6.0 */
382 #define MULTIPLY16C16(var,const) (((INT16) (var)) * ((INT32) (const)))
383 #endif
384
385 #ifndef MULTIPLY16C16 /* default definition */
386 #define MULTIPLY16C16(var,const) ((var) * (const))
387 #endif
388
389 /* Same except both inputs are variables. */
390
391 #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */
392 #define MULTIPLY16V16(var1,var2) (((INT16) (var1)) * ((INT16) (var2)))
393 #endif
394
395 #ifndef MULTIPLY16V16 /* default definition */
396 #define MULTIPLY16V16(var1,var2) ((var1) * (var2))
397 #endif
398
399 /* Like RIGHT_SHIFT, but applies to a DCTELEM.
400 * We assume that int right shift is unsigned if INT32 right shift is.
401 */
402
403 #ifdef RIGHT_SHIFT_IS_UNSIGNED
404 #define ISHIFT_TEMPS DCTELEM ishift_temp;
405 #if BITS_IN_JSAMPLE == 8
406 #define DCTELEMBITS 16 /* DCTELEM may be 16 or 32 bits */
407 #else
408 #define DCTELEMBITS 32 /* DCTELEM must be 32 bits */
409 #endif
410 #define IRIGHT_SHIFT(x,shft) \
411 ((ishift_temp = (x)) < 0 ? \
412 (ishift_temp >> (shft)) | ((~((DCTELEM) 0)) << (DCTELEMBITS-(shft))) : \
413 (ishift_temp >> (shft)))
414 #else
415 #define ISHIFT_TEMPS
416 #define IRIGHT_SHIFT(x,shft) ((x) >> (shft))
417 #endif