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doom3-bfg/neo/libs/jpeg-6/jidctint.cpp
Robert Beckebans c2f45c550c Moved third-party libs to libs/
2012-11-27 21:26:06 +01:00

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/*
* jidctint.c
*
* Copyright (C) 1991-1994, 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.
*/
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h" /* Private declarations for DCT subsystem */
#ifdef DCT_ISLOW_SUPPORTED
/*
* This module is specialized to the case DCTSIZE = 8.
*/
#if DCTSIZE != 8
Sorry, this code only copes with 8 x8 DCTs. /* deliberate syntax err */
#endif
/*
* The poop on this scaling stuff is as follows:
*
* Each 1-D IDCT step produces outputs which are a factor of sqrt(N)
* larger than the true IDCT 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 IDCT,
* because the y0 and y4 inputs need not be divided by sqrt(N).
*
* 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 long 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. (To scale up 12-bit sample data further, an
* intermediate INT32 array would be needed.)
*
* 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.
*/
#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_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) */
#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
/* Multiply an INT32 variable by an INT32 constant to yield an INT32 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.
*/
GLOBAL void
jpeg_idct_islow( j_decompress_ptr cinfo, jpeg_component_info * compptr,
JCOEFPTR coef_block,
JSAMPARRAY output_buf, JDIMENSION output_col ) {
INT32 tmp0, tmp1, tmp2, tmp3;
INT32 tmp10, tmp11, tmp12, tmp13;
INT32 z1, z2, z3, z4, z5;
JCOEFPTR inptr;
ISLOW_MULT_TYPE * quantptr;
int * wsptr;
JSAMPROW outptr;
JSAMPLE * range_limit = IDCT_range_limit( cinfo );
int ctr;
int workspace[DCTSIZE2];/* buffers data between passes */
SHIFT_TEMPS
/* Pass 1: process columns from input, store into work array. */
/* Note results are scaled up by sqrt(8) compared to a true IDCT; */
/* furthermore, we scale the results by 2**PASS1_BITS. */
inptr = coef_block;
quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
wsptr = workspace;
for ( ctr = DCTSIZE; ctr > 0; ctr-- ) {
/* Due to quantization, we will usually find that many of the input
* coefficients are zero, especially the AC terms. We can exploit this
* by short-circuiting the IDCT calculation for any column in which all
* the AC terms are zero. In that case each output is equal to the
* DC coefficient (with scale factor as needed).
* With typical images and quantization tables, half or more of the
* column DCT calculations can be simplified this way.
*/
if ( ( inptr[DCTSIZE * 1] | inptr[DCTSIZE * 2] | inptr[DCTSIZE * 3] |
inptr[DCTSIZE * 4] | inptr[DCTSIZE * 5] | inptr[DCTSIZE * 6] |
inptr[DCTSIZE * 7] ) == 0 ) {
/* AC terms all zero */
int dcval = 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;
wsptr[DCTSIZE * 4] = dcval;
wsptr[DCTSIZE * 5] = dcval;
wsptr[DCTSIZE * 6] = dcval;
wsptr[DCTSIZE * 7] = dcval;
inptr++; /* advance pointers to next column */
quantptr++;
wsptr++;
continue;
}
/* Even part: reverse the even part of the forward DCT. */
/* The rotator is sqrt(2)*c(-6). */
z2 = DEQUANTIZE( inptr[DCTSIZE * 2], quantptr[DCTSIZE * 2] );
z3 = DEQUANTIZE( inptr[DCTSIZE * 6], quantptr[DCTSIZE * 6] );
z1 = MULTIPLY( z2 + z3, FIX_0_541196100 );
tmp2 = z1 + MULTIPLY( z3, -FIX_1_847759065 );
tmp3 = z1 + MULTIPLY( z2, FIX_0_765366865 );
z2 = DEQUANTIZE( inptr[DCTSIZE * 0], quantptr[DCTSIZE * 0] );
z3 = DEQUANTIZE( inptr[DCTSIZE * 4], quantptr[DCTSIZE * 4] );
tmp0 = ( z2 + z3 ) << CONST_BITS;
tmp1 = ( z2 - z3 ) << CONST_BITS;
tmp10 = tmp0 + tmp3;
tmp13 = tmp0 - tmp3;
tmp11 = tmp1 + tmp2;
tmp12 = tmp1 - tmp2;
/* Odd part per figure 8; the matrix is unitary and hence its
* transpose is its inverse. i0..i3 are y7,y5,y3,y1 respectively.
*/
tmp0 = DEQUANTIZE( inptr[DCTSIZE * 7], quantptr[DCTSIZE * 7] );
tmp1 = DEQUANTIZE( inptr[DCTSIZE * 5], quantptr[DCTSIZE * 5] );
tmp2 = DEQUANTIZE( inptr[DCTSIZE * 3], quantptr[DCTSIZE * 3] );
tmp3 = DEQUANTIZE( inptr[DCTSIZE * 1], quantptr[DCTSIZE * 1] );
z1 = tmp0 + tmp3;
z2 = tmp1 + tmp2;
z3 = tmp0 + tmp2;
z4 = tmp1 + tmp3;
z5 = MULTIPLY( z3 + z4, FIX_1_175875602 );/* sqrt(2) * c3 */
tmp0 = MULTIPLY( tmp0, FIX_0_298631336 );/* sqrt(2) * (-c1+c3+c5-c7) */
tmp1 = MULTIPLY( tmp1, FIX_2_053119869 );/* sqrt(2) * ( c1+c3-c5+c7) */
tmp2 = MULTIPLY( tmp2, FIX_3_072711026 );/* sqrt(2) * ( c1+c3+c5-c7) */
tmp3 = MULTIPLY( tmp3, FIX_1_501321110 );/* sqrt(2) * ( c1+c3-c5-c7) */
z1 = MULTIPLY( z1, -FIX_0_899976223 );/* sqrt(2) * (c7-c3) */
z2 = MULTIPLY( z2, -FIX_2_562915447 );/* sqrt(2) * (-c1-c3) */
z3 = MULTIPLY( z3, -FIX_1_961570560 );/* sqrt(2) * (-c3-c5) */
z4 = MULTIPLY( z4, -FIX_0_390180644 );/* sqrt(2) * (c5-c3) */
z3 += z5;
z4 += z5;
tmp0 += z1 + z3;
tmp1 += z2 + z4;
tmp2 += z2 + z3;
tmp3 += z1 + z4;
/* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */
wsptr[DCTSIZE * 0] = (int) DESCALE( tmp10 + tmp3, CONST_BITS - PASS1_BITS );
wsptr[DCTSIZE * 7] = (int) DESCALE( tmp10 - tmp3, CONST_BITS - PASS1_BITS );
wsptr[DCTSIZE * 1] = (int) DESCALE( tmp11 + tmp2, CONST_BITS - PASS1_BITS );
wsptr[DCTSIZE * 6] = (int) DESCALE( tmp11 - tmp2, CONST_BITS - PASS1_BITS );
wsptr[DCTSIZE * 2] = (int) DESCALE( tmp12 + tmp1, CONST_BITS - PASS1_BITS );
wsptr[DCTSIZE * 5] = (int) DESCALE( tmp12 - tmp1, CONST_BITS - PASS1_BITS );
wsptr[DCTSIZE * 3] = (int) DESCALE( tmp13 + tmp0, CONST_BITS - PASS1_BITS );
wsptr[DCTSIZE * 4] = (int) DESCALE( tmp13 - tmp0, CONST_BITS - PASS1_BITS );
inptr++; /* advance pointers to next column */
quantptr++;
wsptr++;
}
/* Pass 2: process rows from work array, store into output array. */
/* Note that we must descale the results by a factor of 8 == 2**3, */
/* and also undo the PASS1_BITS scaling. */
wsptr = workspace;
for ( ctr = 0; ctr < DCTSIZE; ctr++ ) {
outptr = output_buf[ctr] + output_col;
/* Rows of zeroes can be exploited in the same way as we did with columns.
* However, the column calculation has created many nonzero AC terms, so
* the simplification applies less often (typically 5% to 10% of the time).
* On machines with very fast multiplication, it's possible that the
* test takes more time than it's worth. In that case this section
* may be commented out.
*/
#ifndef NO_ZERO_ROW_TEST
if ( ( wsptr[1] | wsptr[2] | wsptr[3] | wsptr[4] | wsptr[5] | wsptr[6] |
wsptr[7] ) == 0 ) {
/* AC terms all zero */
JSAMPLE dcval = range_limit[(int) DESCALE( (INT32) wsptr[0], PASS1_BITS + 3 )
& RANGE_MASK];
outptr[0] = dcval;
outptr[1] = dcval;
outptr[2] = dcval;
outptr[3] = dcval;
outptr[4] = dcval;
outptr[5] = dcval;
outptr[6] = dcval;
outptr[7] = dcval;
wsptr += DCTSIZE;/* advance pointer to next row */
continue;
}
#endif
/* Even part: reverse the even part of the forward DCT. */
/* The rotator is sqrt(2)*c(-6). */
z2 = (INT32) wsptr[2];
z3 = (INT32) wsptr[6];
z1 = MULTIPLY( z2 + z3, FIX_0_541196100 );
tmp2 = z1 + MULTIPLY( z3, -FIX_1_847759065 );
tmp3 = z1 + MULTIPLY( z2, FIX_0_765366865 );
tmp0 = ( (INT32) wsptr[0] + (INT32) wsptr[4] ) << CONST_BITS;
tmp1 = ( (INT32) wsptr[0] - (INT32) wsptr[4] ) << CONST_BITS;
tmp10 = tmp0 + tmp3;
tmp13 = tmp0 - tmp3;
tmp11 = tmp1 + tmp2;
tmp12 = tmp1 - tmp2;
/* Odd part per figure 8; the matrix is unitary and hence its
* transpose is its inverse. i0..i3 are y7,y5,y3,y1 respectively.
*/
tmp0 = (INT32) wsptr[7];
tmp1 = (INT32) wsptr[5];
tmp2 = (INT32) wsptr[3];
tmp3 = (INT32) wsptr[1];
z1 = tmp0 + tmp3;
z2 = tmp1 + tmp2;
z3 = tmp0 + tmp2;
z4 = tmp1 + tmp3;
z5 = MULTIPLY( z3 + z4, FIX_1_175875602 );/* sqrt(2) * c3 */
tmp0 = MULTIPLY( tmp0, FIX_0_298631336 );/* sqrt(2) * (-c1+c3+c5-c7) */
tmp1 = MULTIPLY( tmp1, FIX_2_053119869 );/* sqrt(2) * ( c1+c3-c5+c7) */
tmp2 = MULTIPLY( tmp2, FIX_3_072711026 );/* sqrt(2) * ( c1+c3+c5-c7) */
tmp3 = MULTIPLY( tmp3, FIX_1_501321110 );/* sqrt(2) * ( c1+c3-c5-c7) */
z1 = MULTIPLY( z1, -FIX_0_899976223 );/* sqrt(2) * (c7-c3) */
z2 = MULTIPLY( z2, -FIX_2_562915447 );/* sqrt(2) * (-c1-c3) */
z3 = MULTIPLY( z3, -FIX_1_961570560 );/* sqrt(2) * (-c3-c5) */
z4 = MULTIPLY( z4, -FIX_0_390180644 );/* sqrt(2) * (c5-c3) */
z3 += z5;
z4 += z5;
tmp0 += z1 + z3;
tmp1 += z2 + z4;
tmp2 += z2 + z3;
tmp3 += z1 + z4;
/* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */
outptr[0] = range_limit[(int) DESCALE( tmp10 + tmp3,
CONST_BITS + PASS1_BITS + 3 )
& RANGE_MASK];
outptr[7] = range_limit[(int) DESCALE( tmp10 - tmp3,
CONST_BITS + PASS1_BITS + 3 )
& RANGE_MASK];
outptr[1] = range_limit[(int) DESCALE( tmp11 + tmp2,
CONST_BITS + PASS1_BITS + 3 )
& RANGE_MASK];
outptr[6] = range_limit[(int) DESCALE( tmp11 - tmp2,
CONST_BITS + PASS1_BITS + 3 )
& RANGE_MASK];
outptr[2] = range_limit[(int) DESCALE( tmp12 + tmp1,
CONST_BITS + PASS1_BITS + 3 )
& RANGE_MASK];
outptr[5] = range_limit[(int) DESCALE( tmp12 - tmp1,
CONST_BITS + PASS1_BITS + 3 )
& RANGE_MASK];
outptr[3] = range_limit[(int) DESCALE( tmp13 + tmp0,
CONST_BITS + PASS1_BITS + 3 )
& RANGE_MASK];
outptr[4] = range_limit[(int) DESCALE( tmp13 - tmp0,
CONST_BITS + PASS1_BITS + 3 )
& RANGE_MASK];
wsptr += DCTSIZE; /* advance pointer to next row */
}
}
#endif /* DCT_ISLOW_SUPPORTED */
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