1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
|
/*
* jidctred.c
*
* This file was part of the Independent JPEG Group's software:
* Copyright (C) 1994-1998, Thomas G. Lane.
* libjpeg-turbo Modifications:
* Copyright (C) 2015, D. R. Commander.
* For conditions of distribution and use, see the accompanying README.ijg
* file.
*
* This file contains inverse-DCT routines that produce reduced-size output:
* either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block.
*
* The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M)
* algorithm used in jidctint.c. We simply replace each 8-to-8 1-D IDCT step
* with an 8-to-4 step that produces the four averages of two adjacent outputs
* (or an 8-to-2 step producing two averages of four outputs, for 2x2 output).
* These steps were derived by computing the corresponding values at the end
* of the normal LL&M code, then simplifying as much as possible.
*
* 1x1 is trivial: just take the DC coefficient divided by 8.
*
* See jidctint.c for additional comments.
*/
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h" /* Private declarations for DCT subsystem */
#ifdef IDCT_SCALING_SUPPORTED
/*
* This module is specialized to the case DCTSIZE = 8.
*/
#if DCTSIZE != 8
Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
#endif
/* Scaling is the same as in jidctint.c. */
#if BITS_IN_JSAMPLE == 8
#define CONST_BITS 13
#define PASS1_BITS 2
#else
#define CONST_BITS 13
#define PASS1_BITS 1 /* lose a little precision to avoid overflow */
#endif
/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
* causing a lot of useless floating-point operations at run time.
* To get around this we use the following pre-calculated constants.
* If you change CONST_BITS you may want to add appropriate values.
* (With a reasonable C compiler, you can just rely on the FIX() macro...)
*/
#if CONST_BITS == 13
#define FIX_0_211164243 ((JLONG)1730) /* FIX(0.211164243) */
#define FIX_0_509795579 ((JLONG)4176) /* FIX(0.509795579) */
#define FIX_0_601344887 ((JLONG)4926) /* FIX(0.601344887) */
#define FIX_0_720959822 ((JLONG)5906) /* FIX(0.720959822) */
#define FIX_0_765366865 ((JLONG)6270) /* FIX(0.765366865) */
#define FIX_0_850430095 ((JLONG)6967) /* FIX(0.850430095) */
#define FIX_0_899976223 ((JLONG)7373) /* FIX(0.899976223) */
#define FIX_1_061594337 ((JLONG)8697) /* FIX(1.061594337) */
#define FIX_1_272758580 ((JLONG)10426) /* FIX(1.272758580) */
#define FIX_1_451774981 ((JLONG)11893) /* FIX(1.451774981) */
#define FIX_1_847759065 ((JLONG)15137) /* FIX(1.847759065) */
#define FIX_2_172734803 ((JLONG)17799) /* FIX(2.172734803) */
#define FIX_2_562915447 ((JLONG)20995) /* FIX(2.562915447) */
#define FIX_3_624509785 ((JLONG)29692) /* FIX(3.624509785) */
#else
#define FIX_0_211164243 FIX(0.211164243)
#define FIX_0_509795579 FIX(0.509795579)
#define FIX_0_601344887 FIX(0.601344887)
#define FIX_0_720959822 FIX(0.720959822)
#define FIX_0_765366865 FIX(0.765366865)
#define FIX_0_850430095 FIX(0.850430095)
#define FIX_0_899976223 FIX(0.899976223)
#define FIX_1_061594337 FIX(1.061594337)
#define FIX_1_272758580 FIX(1.272758580)
#define FIX_1_451774981 FIX(1.451774981)
#define FIX_1_847759065 FIX(1.847759065)
#define FIX_2_172734803 FIX(2.172734803)
#define FIX_2_562915447 FIX(2.562915447)
#define FIX_3_624509785 FIX(3.624509785)
#endif
/* Multiply a JLONG variable by a JLONG constant to yield a JLONG result.
* For 8-bit samples with the recommended scaling, all the variable
* and constant values involved are no more than 16 bits wide, so a
* 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
* For 12-bit samples, a full 32-bit multiplication will be needed.
*/
#if BITS_IN_JSAMPLE == 8
#define MULTIPLY(var, const) MULTIPLY16C16(var, const)
#else
#define MULTIPLY(var, const) ((var) * (const))
#endif
/* Dequantize a coefficient by multiplying it by the multiplier-table
* entry; produce an int result. In this module, both inputs and result
* are 16 bits or less, so either int or short multiply will work.
*/
#define DEQUANTIZE(coef, quantval) (((ISLOW_MULT_TYPE)(coef)) * (quantval))
/*
* Perform dequantization and inverse DCT on one block of coefficients,
* producing a reduced-size 4x4 output block.
*/
GLOBAL(void)
jpeg_idct_4x4(j_decompress_ptr cinfo, jpeg_component_info *compptr,
JCOEFPTR coef_block, JSAMPARRAY output_buf,
JDIMENSION output_col)
{
JLONG tmp0, tmp2, tmp10, tmp12;
JLONG z1, z2, z3, z4;
JCOEFPTR inptr;
ISLOW_MULT_TYPE *quantptr;
int *wsptr;
JSAMPROW outptr;
JSAMPLE *range_limit = IDCT_range_limit(cinfo);
int ctr;
int workspace[DCTSIZE * 4]; /* buffers data between passes */
SHIFT_TEMPS
/* Pass 1: process columns from input, store into work array. */
inptr = coef_block;
quantptr = (ISLOW_MULT_TYPE *)compptr->dct_table;
wsptr = workspace;
for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
/* Don't bother to process column 4, because second pass won't use it */
if (ctr == DCTSIZE - 4)
continue;
if (inptr[DCTSIZE * 1] == 0 && inptr[DCTSIZE * 2] == 0 &&
inptr[DCTSIZE * 3] == 0 && inptr[DCTSIZE * 5] == 0 &&
inptr[DCTSIZE * 6] == 0 && inptr[DCTSIZE * 7] == 0) {
/* AC terms all zero; we need not examine term 4 for 4x4 output */
int dcval = LEFT_SHIFT(DEQUANTIZE(inptr[DCTSIZE * 0],
quantptr[DCTSIZE * 0]), PASS1_BITS);
wsptr[DCTSIZE * 0] = dcval;
wsptr[DCTSIZE * 1] = dcval;
wsptr[DCTSIZE * 2] = dcval;
wsptr[DCTSIZE * 3] = dcval;
continue;
}
/* Even part */
tmp0 = DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0]);
tmp0 = LEFT_SHIFT(tmp0, CONST_BITS + 1);
z2 = DEQUANTIZE(inptr[DCTSIZE * 2], quantptr[DCTSIZE * 2]);
z3 = DEQUANTIZE(inptr[DCTSIZE * 6], quantptr[DCTSIZE * 6]);
tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, -FIX_0_765366865);
tmp10 = tmp0 + tmp2;
tmp12 = tmp0 - tmp2;
/* Odd part */
z1 = DEQUANTIZE(inptr[DCTSIZE * 7], quantptr[DCTSIZE * 7]);
z2 = DEQUANTIZE(inptr[DCTSIZE * 5], quantptr[DCTSIZE * 5]);
z3 = DEQUANTIZE(inptr[DCTSIZE * 3], quantptr[DCTSIZE * 3]);
z4 = DEQUANTIZE(inptr[DCTSIZE * 1], quantptr[DCTSIZE * 1]);
tmp0 = MULTIPLY(z1, -FIX_0_211164243) + /* sqrt(2) * ( c3-c1) */
MULTIPLY(z2, FIX_1_451774981) + /* sqrt(2) * ( c3+c7) */
MULTIPLY(z3, -FIX_2_172734803) + /* sqrt(2) * (-c1-c5) */
MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * ( c5+c7) */
tmp2 = MULTIPLY(z1, -FIX_0_509795579) + /* sqrt(2) * (c7-c5) */
MULTIPLY(z2, -FIX_0_601344887) + /* sqrt(2) * (c5-c1) */
MULTIPLY(z3, FIX_0_899976223) + /* sqrt(2) * (c3-c7) */
MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */
/* Final output stage */
wsptr[DCTSIZE * 0] =
(int)DESCALE(tmp10 + tmp2, CONST_BITS - PASS1_BITS + 1);
wsptr[DCTSIZE * 3] =
(int)DESCALE(tmp10 - tmp2, CONST_BITS - PASS1_BITS + 1);
wsptr[DCTSIZE * 1] =
(int)DESCALE(tmp12 + tmp0, CONST_BITS - PASS1_BITS + 1);
wsptr[DCTSIZE * 2] =
(int)DESCALE(tmp12 - tmp0, CONST_BITS - PASS1_BITS + 1);
}
/* Pass 2: process 4 rows from work array, store into output array. */
wsptr = workspace;
for (ctr = 0; ctr < 4; ctr++) {
outptr = output_buf[ctr] + output_col;
/* It's not clear whether a zero row test is worthwhile here ... */
#ifndef NO_ZERO_ROW_TEST
if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 &&
wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
/* AC terms all zero */
JSAMPLE dcval = range_limit[(int)DESCALE((JLONG)wsptr[0],
PASS1_BITS + 3) & RANGE_MASK];
outptr[0] = dcval;
outptr[1] = dcval;
outptr[2] = dcval;
outptr[3] = dcval;
wsptr += DCTSIZE; /* advance pointer to next row */
continue;
}
#endif
/* Even part */
tmp0 = LEFT_SHIFT((JLONG)wsptr[0], CONST_BITS + 1);
tmp2 = MULTIPLY((JLONG)wsptr[2], FIX_1_847759065) +
MULTIPLY((JLONG)wsptr[6], -FIX_0_765366865);
tmp10 = tmp0 + tmp2;
tmp12 = tmp0 - tmp2;
/* Odd part */
z1 = (JLONG)wsptr[7];
z2 = (JLONG)wsptr[5];
z3 = (JLONG)wsptr[3];
z4 = (JLONG)wsptr[1];
tmp0 = MULTIPLY(z1, -FIX_0_211164243) + /* sqrt(2) * ( c3-c1) */
MULTIPLY(z2, FIX_1_451774981) + /* sqrt(2) * ( c3+c7) */
MULTIPLY(z3, -FIX_2_172734803) + /* sqrt(2) * (-c1-c5) */
MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * ( c5+c7) */
tmp2 = MULTIPLY(z1, -FIX_0_509795579) + /* sqrt(2) * (c7-c5) */
MULTIPLY(z2, -FIX_0_601344887) + /* sqrt(2) * (c5-c1) */
MULTIPLY(z3, FIX_0_899976223) + /* sqrt(2) * (c3-c7) */
MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */
/* Final output stage */
outptr[0] = range_limit[(int)DESCALE(tmp10 + tmp2,
CONST_BITS + PASS1_BITS + 3 + 1) &
RANGE_MASK];
outptr[3] = range_limit[(int)DESCALE(tmp10 - tmp2,
CONST_BITS + PASS1_BITS + 3 + 1) &
RANGE_MASK];
outptr[1] = range_limit[(int)DESCALE(tmp12 + tmp0,
CONST_BITS + PASS1_BITS + 3 + 1) &
RANGE_MASK];
outptr[2] = range_limit[(int)DESCALE(tmp12 - tmp0,
CONST_BITS + PASS1_BITS + 3 + 1) &
RANGE_MASK];
wsptr += DCTSIZE; /* advance pointer to next row */
}
}
/*
* Perform dequantization and inverse DCT on one block of coefficients,
* producing a reduced-size 2x2 output block.
*/
GLOBAL(void)
jpeg_idct_2x2(j_decompress_ptr cinfo, jpeg_component_info *compptr,
JCOEFPTR coef_block, JSAMPARRAY output_buf,
JDIMENSION output_col)
{
JLONG tmp0, tmp10, z1;
JCOEFPTR inptr;
ISLOW_MULT_TYPE *quantptr;
int *wsptr;
JSAMPROW outptr;
JSAMPLE *range_limit = IDCT_range_limit(cinfo);
int ctr;
int workspace[DCTSIZE * 2]; /* buffers data between passes */
SHIFT_TEMPS
/* Pass 1: process columns from input, store into work array. */
inptr = coef_block;
quantptr = (ISLOW_MULT_TYPE *)compptr->dct_table;
wsptr = workspace;
for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
/* Don't bother to process columns 2,4,6 */
if (ctr == DCTSIZE - 2 || ctr == DCTSIZE - 4 || ctr == DCTSIZE - 6)
continue;
if (inptr[DCTSIZE * 1] == 0 && inptr[DCTSIZE * 3] == 0 &&
inptr[DCTSIZE * 5] == 0 && inptr[DCTSIZE * 7] == 0) {
/* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */
int dcval = LEFT_SHIFT(DEQUANTIZE(inptr[DCTSIZE * 0],
quantptr[DCTSIZE * 0]), PASS1_BITS);
wsptr[DCTSIZE * 0] = dcval;
wsptr[DCTSIZE * 1] = dcval;
continue;
}
/* Even part */
z1 = DEQUANTIZE(inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0]);
tmp10 = LEFT_SHIFT(z1, CONST_BITS + 2);
/* Odd part */
z1 = DEQUANTIZE(inptr[DCTSIZE * 7], quantptr[DCTSIZE * 7]);
tmp0 = MULTIPLY(z1, -FIX_0_720959822); /* sqrt(2) * ( c7-c5+c3-c1) */
z1 = DEQUANTIZE(inptr[DCTSIZE * 5], quantptr[DCTSIZE * 5]);
tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */
z1 = DEQUANTIZE(inptr[DCTSIZE * 3], quantptr[DCTSIZE * 3]);
tmp0 += MULTIPLY(z1, -FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */
z1 = DEQUANTIZE(inptr[DCTSIZE * 1], quantptr[DCTSIZE * 1]);
tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * ( c1+c3+c5+c7) */
/* Final output stage */
wsptr[DCTSIZE * 0] =
(int)DESCALE(tmp10 + tmp0, CONST_BITS - PASS1_BITS + 2);
wsptr[DCTSIZE * 1] =
(int)DESCALE(tmp10 - tmp0, CONST_BITS - PASS1_BITS + 2);
}
/* Pass 2: process 2 rows from work array, store into output array. */
wsptr = workspace;
for (ctr = 0; ctr < 2; ctr++) {
outptr = output_buf[ctr] + output_col;
/* It's not clear whether a zero row test is worthwhile here ... */
#ifndef NO_ZERO_ROW_TEST
if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) {
/* AC terms all zero */
JSAMPLE dcval = range_limit[(int)DESCALE((JLONG)wsptr[0],
PASS1_BITS + 3) & RANGE_MASK];
outptr[0] = dcval;
outptr[1] = dcval;
wsptr += DCTSIZE; /* advance pointer to next row */
continue;
}
#endif
/* Even part */
tmp10 = LEFT_SHIFT((JLONG)wsptr[0], CONST_BITS + 2);
/* Odd part */
tmp0 = MULTIPLY((JLONG)wsptr[7], -FIX_0_720959822) + /* sqrt(2) * ( c7-c5+c3-c1) */
MULTIPLY((JLONG)wsptr[5], FIX_0_850430095) + /* sqrt(2) * (-c1+c3+c5+c7) */
MULTIPLY((JLONG)wsptr[3], -FIX_1_272758580) + /* sqrt(2) * (-c1+c3-c5-c7) */
MULTIPLY((JLONG)wsptr[1], FIX_3_624509785); /* sqrt(2) * ( c1+c3+c5+c7) */
/* Final output stage */
outptr[0] = range_limit[(int)DESCALE(tmp10 + tmp0,
CONST_BITS + PASS1_BITS + 3 + 2) &
RANGE_MASK];
outptr[1] = range_limit[(int)DESCALE(tmp10 - tmp0,
CONST_BITS + PASS1_BITS + 3 + 2) &
RANGE_MASK];
wsptr += DCTSIZE; /* advance pointer to next row */
}
}
/*
* Perform dequantization and inverse DCT on one block of coefficients,
* producing a reduced-size 1x1 output block.
*/
GLOBAL(void)
jpeg_idct_1x1(j_decompress_ptr cinfo, jpeg_component_info *compptr,
JCOEFPTR coef_block, JSAMPARRAY output_buf,
JDIMENSION output_col)
{
int dcval;
ISLOW_MULT_TYPE *quantptr;
JSAMPLE *range_limit = IDCT_range_limit(cinfo);
SHIFT_TEMPS
/* We hardly need an inverse DCT routine for this: just take the
* average pixel value, which is one-eighth of the DC coefficient.
*/
quantptr = (ISLOW_MULT_TYPE *)compptr->dct_table;
dcval = DEQUANTIZE(coef_block[0], quantptr[0]);
dcval = (int)DESCALE((JLONG)dcval, 3);
output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
}
#endif /* IDCT_SCALING_SUPPORTED */
|
