3rdparty/libjpeg/jfdctflt.c

/*
 * jfdctflt.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 floating-point implementation of the
 * forward DCT (Discrete Cosine Transform).
 *
 * This implementation should be more accurate than either of the integer
 * DCT implementations.  However, it may not give the same results on all
 * machines because of differences in roundoff behavior.  Speed will depend
 * on the hardware's floating point capacity.
 *
 * 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 a fixed-point
 * implementation, accuracy is lost due to imprecise representation of the
 * scaled quantization values.  However, that problem does not arise if
 * we use floating point arithmetic.
 */

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

#ifdef DCT_FLOAT_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


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

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

  /* Pass 1: process rows. */

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

    /* Load data into workspace */
    tmp0 = (FAST_FLOAT) (GETJSAMPLE(elemptr[0]) + GETJSAMPLE(elemptr[7]));
    tmp7 = (FAST_FLOAT) (GETJSAMPLE(elemptr[0]) - GETJSAMPLE(elemptr[7]));
    tmp1 = (FAST_FLOAT) (GETJSAMPLE(elemptr[1]) + GETJSAMPLE(elemptr[6]));
    tmp6 = (FAST_FLOAT) (GETJSAMPLE(elemptr[1]) - GETJSAMPLE(elemptr[6]));
    tmp2 = (FAST_FLOAT) (GETJSAMPLE(elemptr[2]) + GETJSAMPLE(elemptr[5]));
    tmp5 = (FAST_FLOAT) (GETJSAMPLE(elemptr[2]) - GETJSAMPLE(elemptr[5]));
    tmp3 = (FAST_FLOAT) (GETJSAMPLE(elemptr[3]) + GETJSAMPLE(elemptr[4]));
    tmp4 = (FAST_FLOAT) (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 = (tmp12 + tmp13) * ((FAST_FLOAT) 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 = (tmp10 - tmp12) * ((FAST_FLOAT) 0.382683433); /* c6 */
    z2 = ((FAST_FLOAT) 0.541196100) * tmp10 + z5; /* c2-c6 */
    z4 = ((FAST_FLOAT) 1.306562965) * tmp12 + z5; /* c2+c6 */
    z3 = tmp11 * ((FAST_FLOAT) 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 = (tmp12 + tmp13) * ((FAST_FLOAT) 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 = (tmp10 - tmp12) * ((FAST_FLOAT) 0.382683433); /* c6 */
    z2 = ((FAST_FLOAT) 0.541196100) * tmp10 + z5; /* c2-c6 */
    z4 = ((FAST_FLOAT) 1.306562965) * tmp12 + z5; /* c2+c6 */
    z3 = tmp11 * ((FAST_FLOAT) 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_FLOAT_SUPPORTED */
1	/*
2	* jfdctflt.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 floating-point implementation of the
10	* forward DCT (Discrete Cosine Transform).
11	*
12	* This implementation should be more accurate than either of the integer
13	* DCT implementations. However, it may not give the same results on all
14	* machines because of differences in roundoff behavior. Speed will depend
15	* on the hardware's floating point capacity.
16	*
17	* A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT
18	* on each column. Direct algorithms are also available, but they are
19	* much more complex and seem not to be any faster when reduced to code.
20	*
21	* This implementation is based on Arai, Agui, and Nakajima's algorithm for
22	* scaled DCT. Their original paper (Trans. IEICE E-71(11):1095) is in
23	* Japanese, but the algorithm is described in the Pennebaker & Mitchell
24	* JPEG textbook (see REFERENCES section in file README). The following code
25	* is based directly on figure 4-8 in P&M.
26	* While an 8-point DCT cannot be done in less than 11 multiplies, it is
27	* possible to arrange the computation so that many of the multiplies are
28	* simple scalings of the final outputs. These multiplies can then be
29	* folded into the multiplications or divisions by the JPEG quantization
30	* table entries. The AA&N method leaves only 5 multiplies and 29 adds
31	* to be done in the DCT itself.
32	* The primary disadvantage of this method is that with a fixed-point
33	* implementation, accuracy is lost due to imprecise representation of the
34	* scaled quantization values. However, that problem does not arise if
35	* we use floating point arithmetic.
36	*/
37
38	#define JPEG_INTERNALS
39	#include "jinclude.h"
40	#include "jpeglib.h"
41	#include "jdct.h" /* Private declarations for DCT subsystem */
42
43	#ifdef DCT_FLOAT_SUPPORTED
44
45
46	/*
47	* This module is specialized to the case DCTSIZE = 8.
48	*/
49
50	#if DCTSIZE != 8
51	Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
52	#endif
53
54
55	/*
56	* Perform the forward DCT on one block of samples.
57	*/
58
59	GLOBAL(void)
60	jpeg_fdct_float (FAST_FLOAT * data, JSAMPARRAY sample_data, JDIMENSION start_col)
61	{
62	FAST_FLOAT tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
63	FAST_FLOAT tmp10, tmp11, tmp12, tmp13;
64	FAST_FLOAT z1, z2, z3, z4, z5, z11, z13;
65	FAST_FLOAT *dataptr;
66	JSAMPROW elemptr;
67	int ctr;
68
69	/* Pass 1: process rows. */
70
71	dataptr = data;
72	for (ctr = 0; ctr < DCTSIZE; ctr++) {
73	elemptr = sample_data[ctr] + start_col;
74
75	/* Load data into workspace */
76	tmp0 = (FAST_FLOAT) (GETJSAMPLE(elemptr[0]) + GETJSAMPLE(elemptr[7]));
77	tmp7 = (FAST_FLOAT) (GETJSAMPLE(elemptr[0]) - GETJSAMPLE(elemptr[7]));
78	tmp1 = (FAST_FLOAT) (GETJSAMPLE(elemptr[1]) + GETJSAMPLE(elemptr[6]));
79	tmp6 = (FAST_FLOAT) (GETJSAMPLE(elemptr[1]) - GETJSAMPLE(elemptr[6]));
80	tmp2 = (FAST_FLOAT) (GETJSAMPLE(elemptr[2]) + GETJSAMPLE(elemptr[5]));
81	tmp5 = (FAST_FLOAT) (GETJSAMPLE(elemptr[2]) - GETJSAMPLE(elemptr[5]));
82	tmp3 = (FAST_FLOAT) (GETJSAMPLE(elemptr[3]) + GETJSAMPLE(elemptr[4]));
83	tmp4 = (FAST_FLOAT) (GETJSAMPLE(elemptr[3]) - GETJSAMPLE(elemptr[4]));
84
85	/* Even part */
86
87	tmp10 = tmp0 + tmp3; /* phase 2 */
88	tmp13 = tmp0 - tmp3;
89	tmp11 = tmp1 + tmp2;
90	tmp12 = tmp1 - tmp2;
91
92	/* Apply unsigned->signed conversion */
93	dataptr[0] = tmp10 + tmp11 - 8 * CENTERJSAMPLE; /* phase 3 */
94	dataptr[4] = tmp10 - tmp11;
95
96	z1 = (tmp12 + tmp13) * ((FAST_FLOAT) 0.707106781); /* c4 */
97	dataptr[2] = tmp13 + z1; /* phase 5 */
98	dataptr[6] = tmp13 - z1;
99
100	/* Odd part */
101
102	tmp10 = tmp4 + tmp5; /* phase 2 */
103	tmp11 = tmp5 + tmp6;
104	tmp12 = tmp6 + tmp7;
105
106	/* The rotator is modified from fig 4-8 to avoid extra negations. */
107	z5 = (tmp10 - tmp12) * ((FAST_FLOAT) 0.382683433); /* c6 */
108	z2 = ((FAST_FLOAT) 0.541196100) * tmp10 + z5; /* c2-c6 */
109	z4 = ((FAST_FLOAT) 1.306562965) * tmp12 + z5; /* c2+c6 */
110	z3 = tmp11 * ((FAST_FLOAT) 0.707106781); /* c4 */
111
112	z11 = tmp7 + z3; /* phase 5 */
113	z13 = tmp7 - z3;
114
115	dataptr[5] = z13 + z2; /* phase 6 */
116	dataptr[3] = z13 - z2;
117	dataptr[1] = z11 + z4;
118	dataptr[7] = z11 - z4;
119
120	dataptr += DCTSIZE; /* advance pointer to next row */
121	}
122
123	/* Pass 2: process columns. */
124
125	dataptr = data;
126	for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
127	tmp0 = dataptr[DCTSIZE0] + dataptr[DCTSIZE7];
128	tmp7 = dataptr[DCTSIZE0] - dataptr[DCTSIZE7];
129	tmp1 = dataptr[DCTSIZE1] + dataptr[DCTSIZE6];
130	tmp6 = dataptr[DCTSIZE1] - dataptr[DCTSIZE6];
131	tmp2 = dataptr[DCTSIZE2] + dataptr[DCTSIZE5];
132	tmp5 = dataptr[DCTSIZE2] - dataptr[DCTSIZE5];
133	tmp3 = dataptr[DCTSIZE3] + dataptr[DCTSIZE4];
134	tmp4 = dataptr[DCTSIZE3] - dataptr[DCTSIZE4];
135
136	/* Even part */
137
138	tmp10 = tmp0 + tmp3; /* phase 2 */
139	tmp13 = tmp0 - tmp3;
140	tmp11 = tmp1 + tmp2;
141	tmp12 = tmp1 - tmp2;
142
143	dataptr[DCTSIZE0] = tmp10 + tmp11; / phase 3 */
144	dataptr[DCTSIZE*4] = tmp10 - tmp11;
145
146	z1 = (tmp12 + tmp13) * ((FAST_FLOAT) 0.707106781); /* c4 */
147	dataptr[DCTSIZE2] = tmp13 + z1; / phase 5 */
148	dataptr[DCTSIZE*6] = tmp13 - z1;
149
150	/* Odd part */
151
152	tmp10 = tmp4 + tmp5; /* phase 2 */
153	tmp11 = tmp5 + tmp6;
154	tmp12 = tmp6 + tmp7;
155
156	/* The rotator is modified from fig 4-8 to avoid extra negations. */
157	z5 = (tmp10 - tmp12) * ((FAST_FLOAT) 0.382683433); /* c6 */
158	z2 = ((FAST_FLOAT) 0.541196100) * tmp10 + z5; /* c2-c6 */
159	z4 = ((FAST_FLOAT) 1.306562965) * tmp12 + z5; /* c2+c6 */
160	z3 = tmp11 * ((FAST_FLOAT) 0.707106781); /* c4 */
161
162	z11 = tmp7 + z3; /* phase 5 */
163	z13 = tmp7 - z3;
164
165	dataptr[DCTSIZE5] = z13 + z2; / phase 6 */
166	dataptr[DCTSIZE*3] = z13 - z2;
167	dataptr[DCTSIZE*1] = z11 + z4;
168	dataptr[DCTSIZE*7] = z11 - z4;
169
170	dataptr++; /* advance pointer to next column */
171	}
172	}
173
174	#endif /* DCT_FLOAT_SUPPORTED */