/*
* jfdctint.c
*
* Copyright (C) 1991-1996, Thomas G. Lane.
* 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 slow-but-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 an algorithm described in
* C. Loeffler, A. Ligtenberg and G. Moschytz, "Practical Fast 1-D DCT
* Algorithms with 11 Multiplications", Proc. Int'l. Conf. on Acoustics,
* Speech, and Signal Processing 1989 (ICASSP '89), pp. 988-991.
* The primary algorithm described there uses 11 multiplies and 29 adds.
* We use their alternate method with 12 multiplies and 32 adds.
* The advantage of this method is that no data path contains more than one
* multiplication; this allows a very simple and accurate implementation in
* scaled fixed-point arithmetic, with a minimal number of shifts.
*/
#include "jpeg.h"
/*
* The poop on this scaling stuff is as follows:
*
* Each 1-D DCT step produces outputs which are a factor of sqrt(N)
* larger than the true DCT outputs. The final outputs are therefore
* a factor of N larger than desired; since N=8 this can be cured by
* a simple right shift at the end of the algorithm. The advantage of
* this arrangement is that we save two multiplications per 1-D DCT,
* because the y0 and y4 outputs need not be divided by sqrt(N).
* In the IJG code, this factor of 8 is removed by the quantization step
* (in jcdctmgr.c), NOT in this module.
*
* We have to do addition and subtraction of the integer inputs, which
* is no problem, and multiplication by fractional constants, which is
* a problem to do in integer arithmetic. We multiply all the constants
* by CONST_SCALE and convert them to integer constants (thus retaining
* CONST_BITS bits of precision in the constants). After doing a
* multiplication we have to divide the product by CONST_SCALE, with proper
* rounding, to produce the correct output. This division can be done
* cheaply as a right shift of CONST_BITS bits. We postpone shifting
* as int as possible so that partial sums can be added together with
* full fractional precision.
*
* The outputs of the first pass are scaled up by PASS1_BITS bits so that
* they are represented to better-than-integral precision. These outputs
* require BITS_IN_JSAMPLE + PASS1_BITS + 3 bits; this fits in a 16-bit word
* with the recommended scaling. (For 12-bit sample data, the intermediate
* array is INT32 anyway.)
*
* To avoid overflow of the 32-bit intermediate results in pass 2, we must
* have BITS_IN_JSAMPLE + CONST_BITS + PASS1_BITS <= 26. Error analysis
* shows that the values given below are the most effective.
*/
#define CONST_BITS 13
#define PASS1_BITS 2
/* 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_298631336 ((int) 2446) /* FIX(0.298631336) */
#define FIX_0_390180644 ((int) 3196) /* FIX(0.390180644) */
#define FIX_0_541196100 ((int) 4433) /* FIX(0.541196100) */
#define FIX_0_765366865 ((int) 6270) /* FIX(0.765366865) */
#define FIX_0_899976223 ((int) 7373) /* FIX(0.899976223) */
#define FIX_1_175875602 ((int) 9633) /* FIX(1.175875602) */
#define FIX_1_501321110 ((int) 12299) /* FIX(1.501321110) */
#define FIX_1_847759065 ((int) 15137) /* FIX(1.847759065) */
#define FIX_1_961570560 ((int) 16069) /* FIX(1.961570560) */
#define FIX_2_053119869 ((int) 16819) /* FIX(2.053119869) */
#define FIX_2_562915447 ((int) 20995) /* FIX(2.562915447) */
#define FIX_3_072711026 ((int) 25172) /* FIX(3.072711026) */
#else
#define FIX_0_298631336 FIX(0.298631336)
#define FIX_0_390180644 FIX(0.390180644)
#define FIX_0_541196100 FIX(0.541196100)
#define FIX_0_765366865 FIX(0.765366865)
#define FIX_0_899976223 FIX(0.899976223)
#define FIX_1_175875602 FIX(1.175875602)
#define FIX_1_501321110 FIX(1.501321110)
#define FIX_1_847759065 FIX(1.847759065)
#define FIX_1_961570560 FIX(1.961570560)
#define FIX_2_053119869 FIX(2.053119869)
#define FIX_2_562915447 FIX(2.562915447)
#define FIX_3_072711026 FIX(3.072711026)
#endif
/* Convert a positive real constant to an integer scaled by CONST_SCALE.
* Caution: some C compilers fail to reduce "FIX(constant)" at compile time,
* thus causing a lot of useless floating-point operations at run time.
*/
#define FIX(x) ((int) ((x) * (1 << CONST_BITS) + 0.5))
#define RIGHT_SHIFT(x,shft) ((x) >> (shft))
/* Descale and correctly round an INT32 value that's scaled by N bits.
* We assume RIGHT_SHIFT rounds towards minus infinity, so adding
* the fudge factor is correct for either sign of X.
*/
#define DESCALE(x,n) ((short)RIGHT_SHIFT((x) + (1 << ((n)-1)), n))
/*
* Perform an integer forward DCT on one block of samples.
*/
void jpeg_fdct_islow(short * block)
{
int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
int tmp10, tmp11, tmp12, tmp13;
int z1, z2, z3, z4, z5;
short *blkptr;
short *dataptr;
short data[64];
int i;
/* Pass 1: process rows. */
/* Note results are scaled up by sqrt(8) compared to a true DCT; */
/* furthermore, we scale the results by 2**PASS1_BITS. */
dataptr = data;
blkptr = block;
for (i = 0; i < 8; i++)
{
tmp0 = blkptr[0] + blkptr[7];
tmp7 = blkptr[0] - blkptr[7];
tmp1 = blkptr[1] + blkptr[6];
tmp6 = blkptr[1] - blkptr[6];
tmp2 = blkptr[2] + blkptr[5];
tmp5 = blkptr[2] - blkptr[5];
tmp3 = blkptr[3] + blkptr[4];
tmp4 = blkptr[3] - blkptr[4];
/* Even part per LL&M figure 1 --- note that published figure is faulty;
* rotator "sqrt(2)*c1" should be "sqrt(2)*c6".
*/
tmp10 = tmp0 + tmp3;
tmp13 = tmp0 - tmp3;
tmp11 = tmp1 + tmp2;
tmp12 = tmp1 - tmp2;
dataptr[0] = (tmp10 + tmp11) << PASS1_BITS;
dataptr[4] = (tmp10 - tmp11) << PASS1_BITS;
z1 = (tmp12 + tmp13) * FIX_0_541196100;
dataptr[2] = DESCALE(z1 + tmp13 * FIX_0_765366865, CONST_BITS - PASS1_BITS);
dataptr[6] = DESCALE(z1 + tmp12 * (-FIX_1_847759065), CONST_BITS - PASS1_BITS);
/* Odd part per figure 8 --- note paper omits factor of sqrt(2).
* cK represents cos(K*pi/16).
* i0..i3 in the paper are tmp4..tmp7 here.
*/
z1 = tmp4 + tmp7;
z2 = tmp5 + tmp6;
z3 = tmp4 + tmp6;
z4 = tmp5 + tmp7;
z5 = (z3 + z4) * FIX_1_175875602; /* sqrt(2) * c3 */
tmp4 *= FIX_0_298631336; /* sqrt(2) * (-c1+c3+c5-c7) */
tmp5 *= FIX_2_053119869; /* sqrt(2) * ( c1+c3-c5+c7) */
tmp6 *= FIX_3_072711026; /* sqrt(2) * ( c1+c3+c5-c7) */
tmp7 *= FIX_1_501321110; /* sqrt(2) * ( c1+c3-c5-c7) */
z1 *= -FIX_0_899976223; /* sqrt(2) * (c7-c3) */
z2 *= -FIX_2_562915447; /* sqrt(2) * (-c1-c3) */
z3 *= -FIX_1_961570560; /* sqrt(2) * (-c3-c5) */
z4 *= -FIX_0_390180644; /* sqrt(2) * (c5-c3) */
z3 += z5;
z4 += z5;
dataptr[7] = DESCALE(tmp4 + z1 + z3, CONST_BITS - PASS1_BITS);
dataptr[5] = DESCALE(tmp5 + z2 + z4, CONST_BITS - PASS1_BITS);
dataptr[3] = DESCALE(tmp6 + z2 + z3, CONST_BITS - PASS1_BITS);
dataptr[1] = DESCALE(tmp7 + z1 + z4, CONST_BITS - PASS1_BITS);
dataptr += 8; /* advance pointer to next row */
blkptr += 8;
}
/* Pass 2: process columns.
* We remove the PASS1_BITS scaling, but leave the results scaled up
* by an overall factor of 8.
*/
dataptr = data;
for (i = 0; i < 8; i++)
{
tmp0 = dataptr[0] + dataptr[
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JPEG.rar_fft_fft jpeg
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JPEG.rar_fft_fft jpeg (128个子文件)
fdct_mmx_skal.asm 16KB
test.bmp 0B
cjpeg.bsc 57KB
jfdctint.c 23KB
jcparam.c 13KB
jcdctmgr.c 7KB
cjpeg.c 6KB
jcmarker.c 6KB
cjpeg.c 5KB
jchuff.c 5KB
Thumbs.db 71KB
myjpeg.dsp 12KB
cjpeg.dsp 4KB
cjpeglib.dsp 3KB
jpeg.dsw 739B
myjpeg.dsw 535B
djpeg.exe 380KB
cjpeg.exe 268KB
cjpeg.exe 188KB
jpeglib.h 3KB
jpeglib.h 3KB
jpeg.h 2KB
vc60.idb 129KB
vc60.idb 33KB
cjpeg.ilk 191KB
复件 mobile.jpg 31KB
mobile.jpg 31KB
mobile9.jpg 22KB
mobile8.jpg 22KB
mobile2.jpg 22KB
mobile1.jpg 22KB
mobile7.jpg 22KB
mobile0.jpg 22KB
mobile3.jpg 22KB
mobile4.jpg 22KB
mobile6.jpg 22KB
mobile5.jpg 22KB
cjpeglib.lib 59KB
cjpeg.map 51KB
jpeg.ncb 1.03MB
myjpeg.ncb 225KB
jdmarker.obj 34KB
jerror.obj 33KB
djpeg.obj 33KB
cjpeg.obj 30KB
jquant2.obj 26KB
transupp.obj 25KB
wrjpgcom.obj 24KB
jpegtran.obj 23KB
jmemmgr.obj 21KB
rdjpgcom.obj 21KB
jquant1.obj 21KB
jchuff.obj 19KB
jcparam.obj 19KB
ansi2knr.obj 18KB
jcphuff.obj 18KB
jcmarker.obj 18KB
jdcoefct.obj 17KB
ckconfig.obj 17KB
jdphuff.obj 15KB
rdppm.obj 15KB
rdtarga.obj 15KB
jcsample.obj 14KB
jdhuff.obj 14KB
wrgif.obj 14KB
jcmaster.obj 14KB
rdswitch.obj 13KB
jdsample.obj 13KB
cjpeg.obj 13KB
jdmaster.obj 12KB
jccolor.obj 12KB
jdmainct.obj 11KB
jdcolor.obj 11KB
jdapimin.obj 11KB
jctrans.obj 11KB
jdmerge.obj 11KB
jmemname.obj 11KB
jcdctmgr.obj 10KB
jccoefct.obj 10KB
jdinput.obj 10KB
jcapimin.obj 10KB
jmemansi.obj 9KB
jcprepct.obj 9KB
wrtarga.obj 9KB
rdcolmap.obj 9KB
wrppm.obj 8KB
jdapistd.obj 8KB
jdpostct.obj 8KB
jidctred.obj 7KB
example.obj 7KB
jidctflt.obj 7KB
fdct_mmx_skal.obj 7KB
jddctmgr.obj 7KB
jmemnobs.obj 7KB
jidctint.obj 6KB
jidctfst.obj 6KB
jdatasrc.obj 6KB
jcapistd.obj 6KB
jutils.obj 5KB
jdatadst.obj 5KB
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