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mozjpeg/jidctred.c
DRC 123f7258a8 Format copyright headers more consistently 
The IJG convention is to format copyright notices as:

Copyright (C) YYYY, Owner.

We try to maintain this convention for any code that is part of the
libjpeg API library (with the exception of preserving the copyright
notices from Cendio's code verbatim, since those predate
libjpeg-turbo.)

Note that the phrase "All Rights Reserved" is no longer necessary, since
all Buenos Aires Convention signatories signed onto the Berne Convention
in 2000.  However, our convention is to retain this phrase for any files
that have a self-contained copyright header but to leave it off of any
files that refer to another file for conditions of distribution and use.
For instance, all of the non-SIMD files in the libjpeg API library refer
to README.ijg, and the copyright message in that file contains "All
Rights Reserved", so it is unnecessary to add it to the individual
files.

The TurboJPEG code retains my preferred formatting convention for
copyright notices, which is based on that of VirtualGL (where the
TurboJPEG API originated.)
2016-05-28 19:16:58 -05:00

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/*
* jidctred.c
*
* This file was part of the Independent JPEG Group's software.
* Copyright (C) 1994-1998, Thomas G. Lane.
* libjpeg-turbo Modifications:
* Copyright (C) 2015, D. R. Commander.
* For conditions of distribution and use, see the accompanying README.ijg
* file.
*
* This file contains inverse-DCT routines that produce reduced-size output:
* either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block.
*
* The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M)
* algorithm used in jidctint.c. We simply replace each 8-to-8 1-D IDCT step
* with an 8-to-4 step that produces the four averages of two adjacent outputs
* (or an 8-to-2 step producing two averages of four outputs, for 2x2 output).
* These steps were derived by computing the corresponding values at the end
* of the normal LL&M code, then simplifying as much as possible.
*
* 1x1 is trivial: just take the DC coefficient divided by 8.
*
* See jidctint.c for additional comments.
*/
#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h" /* Private declarations for DCT subsystem */
#ifdef IDCT_SCALING_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 is the same as in jidctint.c. */
#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_211164243 ((JLONG) 1730) /* FIX(0.211164243) */
#define FIX_0_509795579 ((JLONG) 4176) /* FIX(0.509795579) */
#define FIX_0_601344887 ((JLONG) 4926) /* FIX(0.601344887) */
#define FIX_0_720959822 ((JLONG) 5906) /* FIX(0.720959822) */
#define FIX_0_765366865 ((JLONG) 6270) /* FIX(0.765366865) */
#define FIX_0_850430095 ((JLONG) 6967) /* FIX(0.850430095) */
#define FIX_0_899976223 ((JLONG) 7373) /* FIX(0.899976223) */
#define FIX_1_061594337 ((JLONG) 8697) /* FIX(1.061594337) */
#define FIX_1_272758580 ((JLONG) 10426) /* FIX(1.272758580) */
#define FIX_1_451774981 ((JLONG) 11893) /* FIX(1.451774981) */
#define FIX_1_847759065 ((JLONG) 15137) /* FIX(1.847759065) */
#define FIX_2_172734803 ((JLONG) 17799) /* FIX(2.172734803) */
#define FIX_2_562915447 ((JLONG) 20995) /* FIX(2.562915447) */
#define FIX_3_624509785 ((JLONG) 29692) /* FIX(3.624509785) */
#else
#define FIX_0_211164243 FIX(0.211164243)
#define FIX_0_509795579 FIX(0.509795579)
#define FIX_0_601344887 FIX(0.601344887)
#define FIX_0_720959822 FIX(0.720959822)
#define FIX_0_765366865 FIX(0.765366865)
#define FIX_0_850430095 FIX(0.850430095)
#define FIX_0_899976223 FIX(0.899976223)
#define FIX_1_061594337 FIX(1.061594337)
#define FIX_1_272758580 FIX(1.272758580)
#define FIX_1_451774981 FIX(1.451774981)
#define FIX_1_847759065 FIX(1.847759065)
#define FIX_2_172734803 FIX(2.172734803)
#define FIX_2_562915447 FIX(2.562915447)
#define FIX_3_624509785 FIX(3.624509785)
#endif
/* Multiply a JLONG variable by a JLONG constant to yield a JLONG 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,
* producing a reduced-size 4x4 output block.
*/
GLOBAL(void)
jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info *compptr,
JCOEFPTR coef_block,
JSAMPARRAY output_buf, JDIMENSION output_col)
{
JLONG tmp0, tmp2, tmp10, tmp12;
JLONG z1, z2, z3, z4;
JCOEFPTR inptr;
ISLOW_MULT_TYPE *quantptr;
int *wsptr;
JSAMPROW outptr;
JSAMPLE *range_limit = IDCT_range_limit(cinfo);
int ctr;
int workspace[DCTSIZE*4]; /* buffers data between passes */
SHIFT_TEMPS
/* Pass 1: process columns from input, store into work array. */
inptr = coef_block;
quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
wsptr = workspace;
for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
/* Don't bother to process column 4, because second pass won't use it */
if (ctr == DCTSIZE-4)
continue;
if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*5] == 0 &&
inptr[DCTSIZE*6] == 0 && inptr[DCTSIZE*7] == 0) {
/* AC terms all zero; we need not examine term 4 for 4x4 output */
int dcval = LEFT_SHIFT(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;
continue;
}
/* Even part */
tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
tmp0 = LEFT_SHIFT(tmp0, CONST_BITS+1);
z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);
tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865);
tmp10 = tmp0 + tmp2;
tmp12 = tmp0 - tmp2;
/* Odd part */
z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
z2 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
z3 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
z4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
+ MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
+ MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
+ MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */
tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
+ MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
+ MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
+ MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */
/* Final output stage */
wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1);
wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1);
wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1);
wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1);
}
/* Pass 2: process 4 rows from work array, store into output array. */
wsptr = workspace;
for (ctr = 0; ctr < 4; ctr++) {
outptr = output_buf[ctr] + output_col;
/* It's not clear whether a zero row test is worthwhile here ... */
#ifndef NO_ZERO_ROW_TEST
if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 &&
wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
/* AC terms all zero */
JSAMPLE dcval = range_limit[(int) DESCALE((JLONG) wsptr[0], PASS1_BITS+3)
& RANGE_MASK];
outptr[0] = dcval;
outptr[1] = dcval;
outptr[2] = dcval;
outptr[3] = dcval;
wsptr += DCTSIZE; /* advance pointer to next row */
continue;
}
#endif
/* Even part */
tmp0 = LEFT_SHIFT((JLONG) wsptr[0], CONST_BITS+1);
tmp2 = MULTIPLY((JLONG) wsptr[2], FIX_1_847759065)
+ MULTIPLY((JLONG) wsptr[6], - FIX_0_765366865);
tmp10 = tmp0 + tmp2;
tmp12 = tmp0 - tmp2;
/* Odd part */
z1 = (JLONG) wsptr[7];
z2 = (JLONG) wsptr[5];
z3 = (JLONG) wsptr[3];
z4 = (JLONG) wsptr[1];
tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
+ MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
+ MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
+ MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */
tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
+ MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
+ MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
+ MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */
/* Final output stage */
outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2,
CONST_BITS+PASS1_BITS+3+1)
& RANGE_MASK];
outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2,
CONST_BITS+PASS1_BITS+3+1)
& RANGE_MASK];
outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0,
CONST_BITS+PASS1_BITS+3+1)
& RANGE_MASK];
outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0,
CONST_BITS+PASS1_BITS+3+1)
& RANGE_MASK];
wsptr += DCTSIZE; /* advance pointer to next row */
}
}
/*
* Perform dequantization and inverse DCT on one block of coefficients,
* producing a reduced-size 2x2 output block.
*/
GLOBAL(void)
jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info *compptr,
JCOEFPTR coef_block,
JSAMPARRAY output_buf, JDIMENSION output_col)
{
JLONG tmp0, tmp10, z1;
JCOEFPTR inptr;
ISLOW_MULT_TYPE *quantptr;
int *wsptr;
JSAMPROW outptr;
JSAMPLE *range_limit = IDCT_range_limit(cinfo);
int ctr;
int workspace[DCTSIZE*2]; /* buffers data between passes */
SHIFT_TEMPS
/* Pass 1: process columns from input, store into work array. */
inptr = coef_block;
quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
wsptr = workspace;
for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
/* Don't bother to process columns 2,4,6 */
if (ctr == DCTSIZE-2 || ctr == DCTSIZE-4 || ctr == DCTSIZE-6)
continue;
if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*3] == 0 &&
inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*7] == 0) {
/* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */
int dcval = LEFT_SHIFT(DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]),
PASS1_BITS);
wsptr[DCTSIZE*0] = dcval;
wsptr[DCTSIZE*1] = dcval;
continue;
}
/* Even part */
z1 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
tmp10 = LEFT_SHIFT(z1, CONST_BITS+2);
/* Odd part */
z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */
z1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */
z1 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */
z1 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */
/* Final output stage */
wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2);
wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2);
}
/* Pass 2: process 2 rows from work array, store into output array. */
wsptr = workspace;
for (ctr = 0; ctr < 2; ctr++) {
outptr = output_buf[ctr] + output_col;
/* It's not clear whether a zero row test is worthwhile here ... */
#ifndef NO_ZERO_ROW_TEST
if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) {
/* AC terms all zero */
JSAMPLE dcval = range_limit[(int) DESCALE((JLONG) wsptr[0], PASS1_BITS+3)
& RANGE_MASK];
outptr[0] = dcval;
outptr[1] = dcval;
wsptr += DCTSIZE; /* advance pointer to next row */
continue;
}
#endif
/* Even part */
tmp10 = LEFT_SHIFT((JLONG) wsptr[0], CONST_BITS+2);
/* Odd part */
tmp0 = MULTIPLY((JLONG) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */
+ MULTIPLY((JLONG) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */
+ MULTIPLY((JLONG) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */
+ MULTIPLY((JLONG) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */
/* Final output stage */
outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0,
CONST_BITS+PASS1_BITS+3+2)
& RANGE_MASK];
outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0,
CONST_BITS+PASS1_BITS+3+2)
& RANGE_MASK];
wsptr += DCTSIZE; /* advance pointer to next row */
}
}
/*
* Perform dequantization and inverse DCT on one block of coefficients,
* producing a reduced-size 1x1 output block.
*/
GLOBAL(void)
jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info *compptr,
JCOEFPTR coef_block,
JSAMPARRAY output_buf, JDIMENSION output_col)
{
int dcval;
ISLOW_MULT_TYPE *quantptr;
JSAMPLE *range_limit = IDCT_range_limit(cinfo);
SHIFT_TEMPS
/* We hardly need an inverse DCT routine for this: just take the
* average pixel value, which is one-eighth of the DC coefficient.
*/
quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
dcval = DEQUANTIZE(coef_block[0], quantptr[0]);
dcval = (int) DESCALE((JLONG) dcval, 3);
output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
}
#endif /* IDCT_SCALING_SUPPORTED */
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