1 #if !defined(_FX_JPEG_TURBO_)
2 /*
3 * jidctred.c
4 *
5 * Copyright (C) 1994-1998, Thomas G. Lane.
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 file contains inverse-DCT routines that produce reduced-size output:
10 * either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block.
11 *
12 * The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M)
13 * algorithm used in jidctint.c. We simply replace each 8-to-8 1-D IDCT step
14 * with an 8-to-4 step that produces the four averages of two adjacent outputs
15 * (or an 8-to-2 step producing two averages of four outputs, for 2x2 output).
16 * These steps were derived by computing the corresponding values at the end
17 * of the normal LL&M code, then simplifying as much as possible.
18 *
19 * 1x1 is trivial: just take the DC coefficient divided by 8.
20 *
21 * See jidctint.c for additional comments.
22 */
23
24 #define JPEG_INTERNALS
25 #include "jinclude.h"
26 #include "jpeglib.h"
27 #include "jdct.h" /* Private declarations for DCT subsystem */
28
29 #ifdef IDCT_SCALING_SUPPORTED
30
31
32 /*
33 * This module is specialized to the case DCTSIZE = 8.
34 */
35
36 #if DCTSIZE != 8
37 Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
38 #endif
39
40
41 /* Scaling is the same as in jidctint.c. */
42
43 #if BITS_IN_JSAMPLE == 8
44 #define CONST_BITS 13
45 #define PASS1_BITS 2
46 #else
47 #define CONST_BITS 13
48 #define PASS1_BITS 1 /* lose a little precision to avoid overflow */
49 #endif
50
51 /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
52 * causing a lot of useless floating-point operations at run time.
53 * To get around this we use the following pre-calculated constants.
54 * If you change CONST_BITS you may want to add appropriate values.
55 * (With a reasonable C compiler, you can just rely on the FIX() macro...)
56 */
57
58 #if CONST_BITS == 13
59 #define FIX_0_211164243 ((INT32) 1730) /* FIX(0.211164243) */
60 #define FIX_0_509795579 ((INT32) 4176) /* FIX(0.509795579) */
61 #define FIX_0_601344887 ((INT32) 4926) /* FIX(0.601344887) */
62 #define FIX_0_720959822 ((INT32) 5906) /* FIX(0.720959822) */
63 #define FIX_0_765366865 ((INT32) 6270) /* FIX(0.765366865) */
64 #define FIX_0_850430095 ((INT32) 6967) /* FIX(0.850430095) */
65 #define FIX_0_899976223 ((INT32) 7373) /* FIX(0.899976223) */
66 #define FIX_1_061594337 ((INT32) 8697) /* FIX(1.061594337) */
67 #define FIX_1_272758580 ((INT32) 10426) /* FIX(1.272758580) */
68 #define FIX_1_451774981 ((INT32) 11893) /* FIX(1.451774981) */
69 #define FIX_1_847759065 ((INT32) 15137) /* FIX(1.847759065) */
70 #define FIX_2_172734803 ((INT32) 17799) /* FIX(2.172734803) */
71 #define FIX_2_562915447 ((INT32) 20995) /* FIX(2.562915447) */
72 #define FIX_3_624509785 ((INT32) 29692) /* FIX(3.624509785) */
73 #else
74 #define FIX_0_211164243 FIX(0.211164243)
75 #define FIX_0_509795579 FIX(0.509795579)
76 #define FIX_0_601344887 FIX(0.601344887)
77 #define FIX_0_720959822 FIX(0.720959822)
78 #define FIX_0_765366865 FIX(0.765366865)
79 #define FIX_0_850430095 FIX(0.850430095)
80 #define FIX_0_899976223 FIX(0.899976223)
81 #define FIX_1_061594337 FIX(1.061594337)
82 #define FIX_1_272758580 FIX(1.272758580)
83 #define FIX_1_451774981 FIX(1.451774981)
84 #define FIX_1_847759065 FIX(1.847759065)
85 #define FIX_2_172734803 FIX(2.172734803)
86 #define FIX_2_562915447 FIX(2.562915447)
87 #define FIX_3_624509785 FIX(3.624509785)
88 #endif
89
90
91 /* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
92 * For 8-bit samples with the recommended scaling, all the variable
93 * and constant values involved are no more than 16 bits wide, so a
94 * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
95 * For 12-bit samples, a full 32-bit multiplication will be needed.
96 */
97
98 #if BITS_IN_JSAMPLE == 8
99 #define MULTIPLY(var,const) MULTIPLY16C16(var,const)
100 #else
101 #define MULTIPLY(var,const) ((var) * (const))
102 #endif
103
104
105 /* Dequantize a coefficient by multiplying it by the multiplier-table
106 * entry; produce an int result. In this module, both inputs and result
107 * are 16 bits or less, so either int or short multiply will work.
108 */
109
110 #define DEQUANTIZE(coef,quantval) (((ISLOW_MULT_TYPE) (coef)) * (quantval))
111
112
113 /*
114 * Perform dequantization and inverse DCT on one block of coefficients,
115 * producing a reduced-size 4x4 output block.
116 */
117
118 GLOBAL(void)
119 jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
120 JCOEFPTR coef_block,
121 JSAMPARRAY output_buf, JDIMENSION output_col)
122 {
123 INT32 tmp0, tmp2, tmp10, tmp12;
124 INT32 z1, z2, z3, z4;
125 JCOEFPTR inptr;
126 ISLOW_MULT_TYPE * quantptr;
127 int * wsptr;
128 JSAMPROW outptr;
129 JSAMPLE *range_limit = IDCT_range_limit(cinfo);
130 int ctr;
131 int workspace[DCTSIZE*4]; /* buffers data between passes */
132 SHIFT_TEMPS
133
134 /* Pass 1: process columns from input, store into work array. */
135
136 inptr = coef_block;
137 quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
138 wsptr = workspace;
139 for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
140 /* Don't bother to process column 4, because second pass won't use it */
141 if (ctr == DCTSIZE-4)
142 continue;
143 if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
144 inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*5] == 0 &&
145 inptr[DCTSIZE*6] == 0 && inptr[DCTSIZE*7] == 0) {
146 /* AC terms all zero; we need not examine term 4 for 4x4 output */
147 int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;
148
149 wsptr[DCTSIZE*0] = dcval;
150 wsptr[DCTSIZE*1] = dcval;
151 wsptr[DCTSIZE*2] = dcval;
152 wsptr[DCTSIZE*3] = dcval;
153
154 continue;
155 }
156
157 /* Even part */
158
159 tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
160 tmp0 <<= (CONST_BITS+1);
161
162 z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
163 z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);
164
165 tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865);
166
167 tmp10 = tmp0 + tmp2;
168 tmp12 = tmp0 - tmp2;
169
170 /* Odd part */
171
172 z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
173 z2 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
174 z3 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
175 z4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
176
177 tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
178 + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
179 + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
180 + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */
181
182 tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
183 + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
184 + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
185 + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */
186
187 /* Final output stage */
188
189 wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1);
190 wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1);
191 wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1);
192 wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1);
193 }
194
195 /* Pass 2: process 4 rows from work array, store into output array. */
196
197 wsptr = workspace;
198 for (ctr = 0; ctr < 4; ctr++) {
199 outptr = output_buf[ctr] + output_col;
200 /* It's not clear whether a zero row test is worthwhile here ... */
201
202 #ifndef NO_ZERO_ROW_TEST
203 if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 &&
204 wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
205 /* AC terms all zero */
206 JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3)
207 & RANGE_MASK];
208
209 outptr[0] = dcval;
210 outptr[1] = dcval;
211 outptr[2] = dcval;
212 outptr[3] = dcval;
213
214 wsptr += DCTSIZE; /* advance pointer to next row */
215 continue;
216 }
217 #endif
218
219 /* Even part */
220
221 tmp0 = ((INT32) wsptr[0]) << (CONST_BITS+1);
222
223 tmp2 = MULTIPLY((INT32) wsptr[2], FIX_1_847759065)
224 + MULTIPLY((INT32) wsptr[6], - FIX_0_765366865);
225
226 tmp10 = tmp0 + tmp2;
227 tmp12 = tmp0 - tmp2;
228
229 /* Odd part */
230
231 z1 = (INT32) wsptr[7];
232 z2 = (INT32) wsptr[5];
233 z3 = (INT32) wsptr[3];
234 z4 = (INT32) wsptr[1];
235
236 tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
237 + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
238 + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
239 + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */
240
241 tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
242 + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
243 + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
244 + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */
245
246 /* Final output stage */
247
248 outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2,
249 CONST_BITS+PASS1_BITS+3+1)
250 & RANGE_MASK];
251 outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2,
252 CONST_BITS+PASS1_BITS+3+1)
253 & RANGE_MASK];
254 outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0,
255 CONST_BITS+PASS1_BITS+3+1)
256 & RANGE_MASK];
257 outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0,
258 CONST_BITS+PASS1_BITS+3+1)
259 & RANGE_MASK];
260
261 wsptr += DCTSIZE; /* advance pointer to next row */
262 }
263 }
264
265
266 /*
267 * Perform dequantization and inverse DCT on one block of coefficients,
268 * producing a reduced-size 2x2 output block.
269 */
270
271 GLOBAL(void)
jpeg_idct_2x2(j_decompress_ptr cinfo,jpeg_component_info * compptr,JCOEFPTR coef_block,JSAMPARRAY output_buf,JDIMENSION output_col)272 jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
273 JCOEFPTR coef_block,
274 JSAMPARRAY output_buf, JDIMENSION output_col)
275 {
276 INT32 tmp0, tmp10, z1;
277 JCOEFPTR inptr;
278 ISLOW_MULT_TYPE * quantptr;
279 int * wsptr;
280 JSAMPROW outptr;
281 JSAMPLE *range_limit = IDCT_range_limit(cinfo);
282 int ctr;
283 int workspace[DCTSIZE*2]; /* buffers data between passes */
284 SHIFT_TEMPS
285
286 /* Pass 1: process columns from input, store into work array. */
287
288 inptr = coef_block;
289 quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
290 wsptr = workspace;
291 for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
292 /* Don't bother to process columns 2,4,6 */
293 if (ctr == DCTSIZE-2 || ctr == DCTSIZE-4 || ctr == DCTSIZE-6)
294 continue;
295 if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*3] == 0 &&
296 inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*7] == 0) {
297 /* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */
298 int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;
299
300 wsptr[DCTSIZE*0] = dcval;
301 wsptr[DCTSIZE*1] = dcval;
302
303 continue;
304 }
305
306 /* Even part */
307
308 z1 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
309 tmp10 = z1 << (CONST_BITS+2);
310
311 /* Odd part */
312
313 z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
314 tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */
315 z1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
316 tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */
317 z1 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
318 tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */
319 z1 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
320 tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */
321
322 /* Final output stage */
323
324 wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2);
325 wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2);
326 }
327
328 /* Pass 2: process 2 rows from work array, store into output array. */
329
330 wsptr = workspace;
331 for (ctr = 0; ctr < 2; ctr++) {
332 outptr = output_buf[ctr] + output_col;
333 /* It's not clear whether a zero row test is worthwhile here ... */
334
335 #ifndef NO_ZERO_ROW_TEST
336 if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) {
337 /* AC terms all zero */
338 JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3)
339 & RANGE_MASK];
340
341 outptr[0] = dcval;
342 outptr[1] = dcval;
343
344 wsptr += DCTSIZE; /* advance pointer to next row */
345 continue;
346 }
347 #endif
348
349 /* Even part */
350
351 tmp10 = ((INT32) wsptr[0]) << (CONST_BITS+2);
352
353 /* Odd part */
354
355 tmp0 = MULTIPLY((INT32) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */
356 + MULTIPLY((INT32) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */
357 + MULTIPLY((INT32) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */
358 + MULTIPLY((INT32) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */
359
360 /* Final output stage */
361
362 outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0,
363 CONST_BITS+PASS1_BITS+3+2)
364 & RANGE_MASK];
365 outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0,
366 CONST_BITS+PASS1_BITS+3+2)
367 & RANGE_MASK];
368
369 wsptr += DCTSIZE; /* advance pointer to next row */
370 }
371 }
372
373
374 /*
375 * Perform dequantization and inverse DCT on one block of coefficients,
376 * producing a reduced-size 1x1 output block.
377 */
378
379 GLOBAL(void)
jpeg_idct_1x1(j_decompress_ptr cinfo,jpeg_component_info * compptr,JCOEFPTR coef_block,JSAMPARRAY output_buf,JDIMENSION output_col)380 jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
381 JCOEFPTR coef_block,
382 JSAMPARRAY output_buf, JDIMENSION output_col)
383 {
384 int dcval;
385 ISLOW_MULT_TYPE * quantptr;
386 JSAMPLE *range_limit = IDCT_range_limit(cinfo);
387 SHIFT_TEMPS
388
389 /* We hardly need an inverse DCT routine for this: just take the
390 * average pixel value, which is one-eighth of the DC coefficient.
391 */
392 quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
393 dcval = DEQUANTIZE(coef_block[0], quantptr[0]);
394 dcval = (int) DESCALE((INT32) dcval, 3);
395
396 output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
397 }
398
399 #endif /* IDCT_SCALING_SUPPORTED */
400
401 #endif //_FX_JPEG_TURBO_
402