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idct.cpp
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idct.cpp
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#ifdef _MSC_VER
#pragma warning(disable:4554)
#pragma warning(disable:4996)
#endif
//
// 2D IDCT
// Derived from an older version of the IJG's JPEG software.
// Downloadable from: www.ijg.org
// This module is going to be replaced with a faster (and
// uncopyrighted) version.
// I am unable to find the original file from which this code was derived.
// I have included the copyright notice included with latest IJG version of this
// module.
//
/*
* jidctint.c
*
* Copyright (C) 1991-1998, 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
* inverse DCT (Discrete Cosine Transform). In the IJG code, this routine
* must also perform dequantization of the input coefficients.
*
* A 2-D IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT
* on each row (or vice versa, but it's more convenient to emit a row at
* a time). 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 "jpegdecoder.h"
/*----------------------------------------------------------------------------*/
#define CONST_BITS 13
#define PASS1_BITS 2
#define SCALEDONE ((int32) 1)
#define CONST_SCALE (SCALEDONE << CONST_BITS)
#define FIX(x) ((int32) ((x) * CONST_SCALE + 0.5))
/*----------------------------------------------------------------------------*/
#define FIX_0_298631336 ((int32) 2446) /* FIX(0.298631336) */
#define FIX_0_390180644 ((int32) 3196) /* FIX(0.390180644) */
#define FIX_0_541196100 ((int32) 4433) /* FIX(0.541196100) */
#define FIX_0_765366865 ((int32) 6270) /* FIX(0.765366865) */
#define FIX_0_899976223 ((int32) 7373) /* FIX(0.899976223) */
#define FIX_1_175875602 ((int32) 9633) /* FIX(1.175875602) */
#define FIX_1_501321110 ((int32) 12299) /* FIX(1.501321110) */
#define FIX_1_847759065 ((int32) 15137) /* FIX(1.847759065) */
#define FIX_1_961570560 ((int32) 16069) /* FIX(1.961570560) */
#define FIX_2_053119869 ((int32) 16819) /* FIX(2.053119869) */
#define FIX_2_562915447 ((int32) 20995) /* FIX(2.562915447) */
#define FIX_3_072711026 ((int32) 25172) /* FIX(3.072711026) */
/*----------------------------------------------------------------------------*/
#define DESCALE(x,n) (((x) + (SCALEDONE << ((n)-1))) >> n)
/*----------------------------------------------------------------------------*/
#define MULTIPLY(var,cnst) ((var) * (cnst))
/*----------------------------------------------------------------------------*/
void idct(BLOCK_TYPE *data, uchar *Pdst_ptr)
{
int32 tmp0, tmp1, tmp2, tmp3;
int32 tmp10, tmp11, tmp12, tmp13;
int32 z1, z2, z3, z4, z5;
register BLOCK_TYPE *dataptr;
int rowctr;
dataptr = data;
for (rowctr = 8-1; rowctr >= 0; rowctr--)
{
if ((dataptr[1] | dataptr[2] | dataptr[3] | dataptr[4] |
dataptr[5] | dataptr[6] | dataptr[7]) == 0)
{
int16 dcval = (int16) (dataptr[0] << PASS1_BITS);
dataptr[0] = dcval;
dataptr[1] = dcval;
dataptr[2] = dcval;
dataptr[3] = dcval;
dataptr[4] = dcval;
dataptr[5] = dcval;
dataptr[6] = dcval;
dataptr[7] = dcval;
dataptr += 8; /* advance pointer to next row */
continue;
}
z2 = (int32) dataptr[2];
z3 = (int32) dataptr[6];
z1 = MULTIPLY(z2 + z3, FIX_0_541196100);
tmp2 = z1 + MULTIPLY(z3, - FIX_1_847759065);
tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865);
tmp0 = ((int32) dataptr[0] + (int32) dataptr[4]) << CONST_BITS;
tmp1 = ((int32) dataptr[0] - (int32) dataptr[4]) << CONST_BITS;
tmp10 = tmp0 + tmp3;
tmp13 = tmp0 - tmp3;
tmp11 = tmp1 + tmp2;
tmp12 = tmp1 - tmp2;
tmp0 = (int32) dataptr[7];
tmp1 = (int32) dataptr[5];
tmp2 = (int32) dataptr[3];
tmp3 = (int32) dataptr[1];
z1 = tmp0 + tmp3;
z2 = tmp1 + tmp2;
z3 = tmp0 + tmp2;
z4 = tmp1 + tmp3;
z5 = MULTIPLY(z3 + z4, FIX_1_175875602);
tmp0 = MULTIPLY(tmp0, FIX_0_298631336);
tmp1 = MULTIPLY(tmp1, FIX_2_053119869);
tmp2 = MULTIPLY(tmp2, FIX_3_072711026);
tmp3 = MULTIPLY(tmp3, FIX_1_501321110);
z1 = MULTIPLY(z1, - FIX_0_899976223);
z2 = MULTIPLY(z2, - FIX_2_562915447);
z3 = MULTIPLY(z3, - FIX_1_961570560);
z4 = MULTIPLY(z4, - FIX_0_390180644);
z3 += z5;
z4 += z5;
tmp0 += z1 + z3;
tmp1 += z2 + z4;
tmp2 += z2 + z3;
tmp3 += z1 + z4;
dataptr[0] = (int16) DESCALE(tmp10 + tmp3, CONST_BITS-PASS1_BITS);
dataptr[7] = (int16) DESCALE(tmp10 - tmp3, CONST_BITS-PASS1_BITS);
dataptr[1] = (int16) DESCALE(tmp11 + tmp2, CONST_BITS-PASS1_BITS);
dataptr[6] = (int16) DESCALE(tmp11 - tmp2, CONST_BITS-PASS1_BITS);
dataptr[2] = (int16) DESCALE(tmp12 + tmp1, CONST_BITS-PASS1_BITS);
dataptr[5] = (int16) DESCALE(tmp12 - tmp1, CONST_BITS-PASS1_BITS);
dataptr[3] = (int16) DESCALE(tmp13 + tmp0, CONST_BITS-PASS1_BITS);
dataptr[4] = (int16) DESCALE(tmp13 - tmp0, CONST_BITS-PASS1_BITS);
dataptr += 8;
}
dataptr = data;
for (rowctr = 8-1; rowctr >= 0; rowctr--)
{
int16 i;
if ((dataptr[8*1] | dataptr[8*2] | dataptr[8*3] |
dataptr[8*4] | dataptr[8*5] | dataptr[8*6] |
dataptr[8*7]) == 0)
{
int16 dcval = (int16) DESCALE((int32) dataptr[0], PASS1_BITS+3);
if ((dcval += 128) < 0)
dcval = 0;
else if (dcval > 255)
dcval = 255;
Pdst_ptr[8*0] = (uchar)dcval;
Pdst_ptr[8*1] = (uchar)dcval;
Pdst_ptr[8*2] = (uchar)dcval;
Pdst_ptr[8*3] = (uchar)dcval;
Pdst_ptr[8*4] = (uchar)dcval;
Pdst_ptr[8*5] = (uchar)dcval;
Pdst_ptr[8*6] = (uchar)dcval;
Pdst_ptr[8*7] = (uchar)dcval;
dataptr++;
Pdst_ptr++;
continue;
}
z2 = (int32) dataptr[8*2];
z3 = (int32) dataptr[8*6];
z1 = MULTIPLY(z2 + z3, FIX_0_541196100);
tmp2 = z1 + MULTIPLY(z3, - FIX_1_847759065);
tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865);
tmp0 = ((int32) dataptr[8*0] + (int32) dataptr[8*4]) << CONST_BITS;
tmp1 = ((int32) dataptr[8*0] - (int32) dataptr[8*4]) << CONST_BITS;
tmp10 = tmp0 + tmp3;
tmp13 = tmp0 - tmp3;
tmp11 = tmp1 + tmp2;
tmp12 = tmp1 - tmp2;
tmp0 = (int32) dataptr[8*7];
tmp1 = (int32) dataptr[8*5];
tmp2 = (int32) dataptr[8*3];
tmp3 = (int32) dataptr[8*1];
z1 = tmp0 + tmp3;
z2 = tmp1 + tmp2;
z3 = tmp0 + tmp2;
z4 = tmp1 + tmp3;
z5 = MULTIPLY(z3 + z4, FIX_1_175875602);
tmp0 = MULTIPLY(tmp0, FIX_0_298631336);
tmp1 = MULTIPLY(tmp1, FIX_2_053119869);
tmp2 = MULTIPLY(tmp2, FIX_3_072711026);
tmp3 = MULTIPLY(tmp3, FIX_1_501321110);
z1 = MULTIPLY(z1, - FIX_0_899976223);
z2 = MULTIPLY(z2, - FIX_2_562915447);
z3 = MULTIPLY(z3, - FIX_1_961570560);
z4 = MULTIPLY(z4, - FIX_0_390180644);
z3 += z5;
z4 += z5;
tmp0 += z1 + z3;
tmp1 += z2 + z4;
tmp2 += z2 + z3;
tmp3 += z1 + z4;
#define clamp(i) if (i & 0xFF00) i = (((~i) >> 15) & 0xFF);
i = (int16) DESCALE(tmp10 + tmp3, CONST_BITS+PASS1_BITS+3) + 128;
clamp(i)
Pdst_ptr[8*0] = (uchar)i;
i = (int16) DESCALE(tmp10 - tmp3, CONST_BITS+PASS1_BITS+3) + 128;
clamp(i)
Pdst_ptr[8*7] = (uchar)i;
i = (int16) DESCALE(tmp11 + tmp2, CONST_BITS+PASS1_BITS+3) + 128;
clamp(i)
Pdst_ptr[8*1] = (uchar)i;
i = (int16) DESCALE(tmp11 - tmp2, CONST_BITS+PASS1_BITS+3) + 128;
clamp(i)
Pdst_ptr[8*6] = (uchar)i;
i = (int16) DESCALE(tmp12 + tmp1, CONST_BITS+PASS1_BITS+3) + 128;
clamp(i)
Pdst_ptr[8*2] = (uchar)i;
i = (int16) DESCALE(tmp12 - tmp1, CONST_BITS+PASS1_BITS+3) + 128;
clamp(i)
Pdst_ptr[8*5] = (uchar)i;
i = (int16) DESCALE(tmp13 + tmp0, CONST_BITS+PASS1_BITS+3) + 128;
clamp(i)
Pdst_ptr[8*3] = (uchar)i;
i = (int16) DESCALE(tmp13 - tmp0, CONST_BITS+PASS1_BITS+3) + 128;
clamp(i)
Pdst_ptr[8*4] = (uchar)i;
dataptr++;
Pdst_ptr++;
}
}
/*----------------------------------------------------------------------------*/