3rdparty/libjpeg/jfdctfst.c

/*
 * jfdctfst.c
 *
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * Modified 2003-2009 by Guido Vollbeding.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains a fast, not so accurate integer implementation of the
 * forward DCT (Discrete Cosine Transform).
 *
 * A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT
 * on each column.  Direct algorithms are also available, but they are
 * much more complex and seem not to be any faster when reduced to code.
 *
 * This implementation is based on Arai, Agui, and Nakajima's algorithm for
 * scaled DCT.  Their original paper (Trans. IEICE E-71(11):1095) is in
 * Japanese, but the algorithm is described in the Pennebaker & Mitchell
 * JPEG textbook (see REFERENCES section in file README).  The following code
 * is based directly on figure 4-8 in P&M.
 * While an 8-point DCT cannot be done in less than 11 multiplies, it is
 * possible to arrange the computation so that many of the multiplies are
 * simple scalings of the final outputs.  These multiplies can then be
 * folded into the multiplications or divisions by the JPEG quantization
 * table entries.  The AA&N method leaves only 5 multiplies and 29 adds
 * to be done in the DCT itself.
 * The primary disadvantage of this method is that with fixed-point math,
 * accuracy is lost due to imprecise representation of the scaled
 * quantization values.  The smaller the quantization table entry, the less
 * precise the scaled value, so this implementation does worse with high-
 * quality-setting files than with low-quality ones.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h"               /* Private declarations for DCT subsystem */

#ifdef DCT_IFAST_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 decisions are generally the same as in the LL&M algorithm;
 * see jfdctint.c for more details.  However, we choose to descale
 * (right shift) multiplication products as soon as they are formed,
 * rather than carrying additional fractional bits into subsequent additions.
 * This compromises accuracy slightly, but it lets us save a few shifts.
 * More importantly, 16-bit arithmetic is then adequate (for 8-bit samples)
 * everywhere except in the multiplications proper; this saves a good deal
 * of work on 16-bit-int machines.
 *
 * Again to save a few shifts, the intermediate results between pass 1 and
 * pass 2 are not upscaled, but are represented only to integral precision.
 *
 * A final compromise is to represent the multiplicative constants to only
 * 8 fractional bits, rather than 13.  This saves some shifting work on some
 * machines, and may also reduce the cost of multiplication (since there
 * are fewer one-bits in the constants).
 */

#define CONST_BITS  8


/* 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 == 8
#define FIX_0_382683433  ((INT32)   98)         /* FIX(0.382683433) */
#define FIX_0_541196100  ((INT32)  139)         /* FIX(0.541196100) */
#define FIX_0_707106781  ((INT32)  181)         /* FIX(0.707106781) */
#define FIX_1_306562965  ((INT32)  334)         /* FIX(1.306562965) */
#else
#define FIX_0_382683433  FIX(0.382683433)
#define FIX_0_541196100  FIX(0.541196100)
#define FIX_0_707106781  FIX(0.707106781)
#define FIX_1_306562965  FIX(1.306562965)
#endif


/* We can gain a little more speed, with a further compromise in accuracy,
 * by omitting the addition in a descaling shift.  This yields an incorrectly
 * rounded result half the time...
 */

#ifndef USE_ACCURATE_ROUNDING
#undef DESCALE
#define DESCALE(x,n)  RIGHT_SHIFT(x, n)
#endif


/* Multiply a DCTELEM variable by an INT32 constant, and immediately
 * descale to yield a DCTELEM result.
 */

#define MULTIPLY(var,const)  ((DCTELEM) DESCALE((var) * (const), CONST_BITS))


/*
 * Perform the forward DCT on one block of samples.
 */

GLOBAL(void)
jpeg_fdct_ifast (DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)
{
  DCTELEM tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
  DCTELEM tmp10, tmp11, tmp12, tmp13;
  DCTELEM z1, z2, z3, z4, z5, z11, z13;
  DCTELEM *dataptr;
  JSAMPROW elemptr;
  int ctr;
  SHIFT_TEMPS

  /* Pass 1: process rows. */

  dataptr = data;
  for (ctr = 0; ctr < DCTSIZE; ctr++) {
    elemptr = sample_data[ctr] + start_col;

    /* Load data into workspace */
    tmp0 = GETJSAMPLE(elemptr[0]) + GETJSAMPLE(elemptr[7]);
    tmp7 = GETJSAMPLE(elemptr[0]) - GETJSAMPLE(elemptr[7]);
    tmp1 = GETJSAMPLE(elemptr[1]) + GETJSAMPLE(elemptr[6]);
    tmp6 = GETJSAMPLE(elemptr[1]) - GETJSAMPLE(elemptr[6]);
    tmp2 = GETJSAMPLE(elemptr[2]) + GETJSAMPLE(elemptr[5]);
    tmp5 = GETJSAMPLE(elemptr[2]) - GETJSAMPLE(elemptr[5]);
    tmp3 = GETJSAMPLE(elemptr[3]) + GETJSAMPLE(elemptr[4]);
    tmp4 = GETJSAMPLE(elemptr[3]) - GETJSAMPLE(elemptr[4]);

    /* Even part */

    tmp10 = tmp0 + tmp3;        /* phase 2 */
    tmp13 = tmp0 - tmp3;
    tmp11 = tmp1 + tmp2;
    tmp12 = tmp1 - tmp2;

    /* Apply unsigned->signed conversion */
    dataptr[0] = tmp10 + tmp11 - 8 * CENTERJSAMPLE; /* phase 3 */
    dataptr[4] = tmp10 - tmp11;

    z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */
    dataptr[2] = tmp13 + z1;    /* phase 5 */
    dataptr[6] = tmp13 - z1;

    /* Odd part */

    tmp10 = tmp4 + tmp5;        /* phase 2 */
    tmp11 = tmp5 + tmp6;
    tmp12 = tmp6 + tmp7;

    /* The rotator is modified from fig 4-8 to avoid extra negations. */
    z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */
    z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */
    z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */
    z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */

    z11 = tmp7 + z3;            /* phase 5 */
    z13 = tmp7 - z3;

    dataptr[5] = z13 + z2;      /* phase 6 */
    dataptr[3] = z13 - z2;
    dataptr[1] = z11 + z4;
    dataptr[7] = z11 - z4;

    dataptr += DCTSIZE;         /* advance pointer to next row */
  }

  /* Pass 2: process columns. */

  dataptr = data;
  for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
    tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*7];
    tmp7 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*7];
    tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*6];
    tmp6 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*6];
    tmp2 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*5];
    tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*5];
    tmp3 = dataptr[DCTSIZE*3] + dataptr[DCTSIZE*4];
    tmp4 = dataptr[DCTSIZE*3] - dataptr[DCTSIZE*4];

    /* Even part */

    tmp10 = tmp0 + tmp3;        /* phase 2 */
    tmp13 = tmp0 - tmp3;
    tmp11 = tmp1 + tmp2;
    tmp12 = tmp1 - tmp2;

    dataptr[DCTSIZE*0] = tmp10 + tmp11; /* phase 3 */
    dataptr[DCTSIZE*4] = tmp10 - tmp11;

    z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */
    dataptr[DCTSIZE*2] = tmp13 + z1; /* phase 5 */
    dataptr[DCTSIZE*6] = tmp13 - z1;

    /* Odd part */

    tmp10 = tmp4 + tmp5;        /* phase 2 */
    tmp11 = tmp5 + tmp6;
    tmp12 = tmp6 + tmp7;

    /* The rotator is modified from fig 4-8 to avoid extra negations. */
    z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */
    z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */
    z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */
    z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */

    z11 = tmp7 + z3;            /* phase 5 */
    z13 = tmp7 - z3;

    dataptr[DCTSIZE*5] = z13 + z2; /* phase 6 */
    dataptr[DCTSIZE*3] = z13 - z2;
    dataptr[DCTSIZE*1] = z11 + z4;
    dataptr[DCTSIZE*7] = z11 - z4;

    dataptr++;                  /* advance pointer to next column */
  }
}

#endif /* DCT_IFAST_SUPPORTED */
1	/*
2	* jfdctfst.c
3	*
4	* Copyright (C) 1994-1996, Thomas G. Lane.
5	* Modified 2003-2009 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 file contains a fast, not so accurate integer implementation of the
10	* forward DCT (Discrete Cosine Transform).
11	*
12	* A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT
13	* on each column. Direct algorithms are also available, but they are
14	* much more complex and seem not to be any faster when reduced to code.
15	*
16	* This implementation is based on Arai, Agui, and Nakajima's algorithm for
17	* scaled DCT. Their original paper (Trans. IEICE E-71(11):1095) is in
18	* Japanese, but the algorithm is described in the Pennebaker & Mitchell
19	* JPEG textbook (see REFERENCES section in file README). The following code
20	* is based directly on figure 4-8 in P&M.
21	* While an 8-point DCT cannot be done in less than 11 multiplies, it is
22	* possible to arrange the computation so that many of the multiplies are
23	* simple scalings of the final outputs. These multiplies can then be
24	* folded into the multiplications or divisions by the JPEG quantization
25	* table entries. The AA&N method leaves only 5 multiplies and 29 adds
26	* to be done in the DCT itself.
27	* The primary disadvantage of this method is that with fixed-point math,
28	* accuracy is lost due to imprecise representation of the scaled
29	* quantization values. The smaller the quantization table entry, the less
30	* precise the scaled value, so this implementation does worse with high-
31	* quality-setting files than with low-quality ones.
32	*/
33
34	#define JPEG_INTERNALS
35	#include "jinclude.h"
36	#include "jpeglib.h"
37	#include "jdct.h" /* Private declarations for DCT subsystem */
38
39	#ifdef DCT_IFAST_SUPPORTED
40
41
42	/*
43	* This module is specialized to the case DCTSIZE = 8.
44	*/
45
46	#if DCTSIZE != 8
47	Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
48	#endif
49
50
51	/* Scaling decisions are generally the same as in the LL&M algorithm;
52	* see jfdctint.c for more details. However, we choose to descale
53	* (right shift) multiplication products as soon as they are formed,
54	* rather than carrying additional fractional bits into subsequent additions.
55	* This compromises accuracy slightly, but it lets us save a few shifts.
56	* More importantly, 16-bit arithmetic is then adequate (for 8-bit samples)
57	* everywhere except in the multiplications proper; this saves a good deal
58	* of work on 16-bit-int machines.
59	*
60	* Again to save a few shifts, the intermediate results between pass 1 and
61	* pass 2 are not upscaled, but are represented only to integral precision.
62	*
63	* A final compromise is to represent the multiplicative constants to only
64	* 8 fractional bits, rather than 13. This saves some shifting work on some
65	* machines, and may also reduce the cost of multiplication (since there
66	* are fewer one-bits in the constants).
67	*/
68
69	#define CONST_BITS 8
70
71
72	/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
73	* causing a lot of useless floating-point operations at run time.
74	* To get around this we use the following pre-calculated constants.
75	* If you change CONST_BITS you may want to add appropriate values.
76	* (With a reasonable C compiler, you can just rely on the FIX() macro...)
77	*/
78
79	#if CONST_BITS == 8
80	#define FIX_0_382683433 ((INT32) 98) /* FIX(0.382683433) */
81	#define FIX_0_541196100 ((INT32) 139) /* FIX(0.541196100) */
82	#define FIX_0_707106781 ((INT32) 181) /* FIX(0.707106781) */
83	#define FIX_1_306562965 ((INT32) 334) /* FIX(1.306562965) */
84	#else
85	#define FIX_0_382683433 FIX(0.382683433)
86	#define FIX_0_541196100 FIX(0.541196100)
87	#define FIX_0_707106781 FIX(0.707106781)
88	#define FIX_1_306562965 FIX(1.306562965)
89	#endif
90
91
92	/* We can gain a little more speed, with a further compromise in accuracy,
93	* by omitting the addition in a descaling shift. This yields an incorrectly
94	* rounded result half the time...
95	*/
96
97	#ifndef USE_ACCURATE_ROUNDING
98	#undef DESCALE
99	#define DESCALE(x,n) RIGHT_SHIFT(x, n)
100	#endif
101
102
103	/* Multiply a DCTELEM variable by an INT32 constant, and immediately
104	* descale to yield a DCTELEM result.
105	*/
106
107	#define MULTIPLY(var,const) ((DCTELEM) DESCALE((var) * (const), CONST_BITS))
108
109
110	/*
111	* Perform the forward DCT on one block of samples.
112	*/
113
114	GLOBAL(void)
115	jpeg_fdct_ifast (DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)
116	{
117	DCTELEM tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
118	DCTELEM tmp10, tmp11, tmp12, tmp13;
119	DCTELEM z1, z2, z3, z4, z5, z11, z13;
120	DCTELEM *dataptr;
121	JSAMPROW elemptr;
122	int ctr;
123	SHIFT_TEMPS
124
125	/* Pass 1: process rows. */
126
127	dataptr = data;
128	for (ctr = 0; ctr < DCTSIZE; ctr++) {
129	elemptr = sample_data[ctr] + start_col;
130
131	/* Load data into workspace */
132	tmp0 = GETJSAMPLE(elemptr[0]) + GETJSAMPLE(elemptr[7]);
133	tmp7 = GETJSAMPLE(elemptr[0]) - GETJSAMPLE(elemptr[7]);
134	tmp1 = GETJSAMPLE(elemptr[1]) + GETJSAMPLE(elemptr[6]);
135	tmp6 = GETJSAMPLE(elemptr[1]) - GETJSAMPLE(elemptr[6]);
136	tmp2 = GETJSAMPLE(elemptr[2]) + GETJSAMPLE(elemptr[5]);
137	tmp5 = GETJSAMPLE(elemptr[2]) - GETJSAMPLE(elemptr[5]);
138	tmp3 = GETJSAMPLE(elemptr[3]) + GETJSAMPLE(elemptr[4]);
139	tmp4 = GETJSAMPLE(elemptr[3]) - GETJSAMPLE(elemptr[4]);
140
141	/* Even part */
142
143	tmp10 = tmp0 + tmp3; /* phase 2 */
144	tmp13 = tmp0 - tmp3;
145	tmp11 = tmp1 + tmp2;
146	tmp12 = tmp1 - tmp2;
147
148	/* Apply unsigned->signed conversion */
149	dataptr[0] = tmp10 + tmp11 - 8 * CENTERJSAMPLE; /* phase 3 */
150	dataptr[4] = tmp10 - tmp11;
151
152	z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */
153	dataptr[2] = tmp13 + z1; /* phase 5 */
154	dataptr[6] = tmp13 - z1;
155
156	/* Odd part */
157
158	tmp10 = tmp4 + tmp5; /* phase 2 */
159	tmp11 = tmp5 + tmp6;
160	tmp12 = tmp6 + tmp7;
161
162	/* The rotator is modified from fig 4-8 to avoid extra negations. */
163	z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */
164	z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */
165	z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */
166	z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */
167
168	z11 = tmp7 + z3; /* phase 5 */
169	z13 = tmp7 - z3;
170
171	dataptr[5] = z13 + z2; /* phase 6 */
172	dataptr[3] = z13 - z2;
173	dataptr[1] = z11 + z4;
174	dataptr[7] = z11 - z4;
175
176	dataptr += DCTSIZE; /* advance pointer to next row */
177	}
178
179	/* Pass 2: process columns. */
180
181	dataptr = data;
182	for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
183	tmp0 = dataptr[DCTSIZE0] + dataptr[DCTSIZE7];
184	tmp7 = dataptr[DCTSIZE0] - dataptr[DCTSIZE7];
185	tmp1 = dataptr[DCTSIZE1] + dataptr[DCTSIZE6];
186	tmp6 = dataptr[DCTSIZE1] - dataptr[DCTSIZE6];
187	tmp2 = dataptr[DCTSIZE2] + dataptr[DCTSIZE5];
188	tmp5 = dataptr[DCTSIZE2] - dataptr[DCTSIZE5];
189	tmp3 = dataptr[DCTSIZE3] + dataptr[DCTSIZE4];
190	tmp4 = dataptr[DCTSIZE3] - dataptr[DCTSIZE4];
191
192	/* Even part */
193
194	tmp10 = tmp0 + tmp3; /* phase 2 */
195	tmp13 = tmp0 - tmp3;
196	tmp11 = tmp1 + tmp2;
197	tmp12 = tmp1 - tmp2;
198
199	dataptr[DCTSIZE0] = tmp10 + tmp11; / phase 3 */
200	dataptr[DCTSIZE*4] = tmp10 - tmp11;
201
202	z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */
203	dataptr[DCTSIZE2] = tmp13 + z1; / phase 5 */
204	dataptr[DCTSIZE*6] = tmp13 - z1;
205
206	/* Odd part */
207
208	tmp10 = tmp4 + tmp5; /* phase 2 */
209	tmp11 = tmp5 + tmp6;
210	tmp12 = tmp6 + tmp7;
211
212	/* The rotator is modified from fig 4-8 to avoid extra negations. */
213	z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */
214	z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */
215	z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */
216	z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */
217
218	z11 = tmp7 + z3; /* phase 5 */
219	z13 = tmp7 - z3;
220
221	dataptr[DCTSIZE5] = z13 + z2; / phase 6 */
222	dataptr[DCTSIZE*3] = z13 - z2;
223	dataptr[DCTSIZE*1] = z11 + z4;
224	dataptr[DCTSIZE*7] = z11 - z4;
225
226	dataptr++; /* advance pointer to next column */
227	}
228	}
229
230	#endif /* DCT_IFAST_SUPPORTED */