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/*
* jdpred.c
*
* Copyright (C) 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 sample undifferencing (reconstruction) for lossless JPEG.
*
* In order to avoid paying the performance penalty of having to check the
* predictor being used and the row being processed for each call of the
* undifferencer, and to promote optimization, we have separate undifferencing
* functions for each case.
*
* We are able to avoid duplicating source code by implementing the predictors
* and undifferencers as macros. Each of the undifferencing functions are
* simply wrappers around an UNDIFFERENCE macro with the appropriate PREDICTOR
* macro passed as an argument.
*/
#define JPEG_INTERNALS
#include "jinclude16.h"
#include "jpeglib16.h"
#include "jlossls16.h" /* Private declarations for lossless codec */
#ifdef D_LOSSLESS_SUPPORTED
/* Predictor for the first column of the first row: 2^(P-Pt-1) */
#define INITIAL_PREDICTORx (1 << (cinfo->data_precision - cinfo->Al - 1))
/* Predictor for the first column of the remaining rows: Rb */
#define INITIAL_PREDICTOR2 GETJSAMPLE(prev_row[0])
/*
* 1-Dimensional undifferencer routine.
*
* This macro implements the 1-D horizontal predictor (1). INITIAL_PREDICTOR
* is used as the special case predictor for the first column, which must be
* either INITIAL_PREDICTOR2 or INITIAL_PREDICTORx. The remaining samples
* use PREDICTOR1.
*
* The reconstructed sample is supposed to be calculated modulo 2^16, so we
* logically AND the result with 0xFFFF.
*/
#define UNDIFFERENCE_1D(INITIAL_PREDICTOR) \
unsigned int xindex; \
int Ra; \
\
Ra = (diff_buf[0] + INITIAL_PREDICTOR) & 0xFFFF; \
undiff_buf[0] = Ra; \
\
for (xindex = 1; xindex < width; xindex++) { \
Ra = (diff_buf[xindex] + PREDICTOR1) & 0xFFFF; \
undiff_buf[xindex] = Ra; \
}
/*
* 2-Dimensional undifferencer routine.
*
* This macro implements the 2-D horizontal predictors (#2-7). PREDICTOR2 is
* used as the special case predictor for the first column. The remaining
* samples use PREDICTOR, which is a function of Ra, Rb, Rc.
*
* Because prev_row and output_buf may point to the same storage area (in an
* interleaved image with Vi=1, for example), we must take care to buffer Rb/Rc
* before writing the current reconstructed sample value into output_buf.
*
* The reconstructed sample is supposed to be calculated modulo 2^16, so we
* logically AND the result with 0xFFFF.
*/
#define UNDIFFERENCE_2D(PREDICTOR) \
unsigned int xindex; \
int Ra, Rb, Rc; \
\
Rb = GETJSAMPLE(prev_row[0]); \
Ra = (diff_buf[0] + PREDICTOR2) & 0xFFFF; \
undiff_buf[0] = Ra; \
\
for (xindex = 1; xindex < width; xindex++) { \
Rc = Rb; \
Rb = GETJSAMPLE(prev_row[xindex]); \
Ra = (diff_buf[xindex] + PREDICTOR) & 0xFFFF; \
undiff_buf[xindex] = Ra; \
}
/*
* Undifferencers for the all rows but the first in a scan or restart interval.
* The first sample in the row is undifferenced using the vertical
* predictor (2). The rest of the samples are undifferenced using the
* predictor specified in the scan header.
*/
METHODDEF(void)
jpeg_undifference1(j_decompress_ptr cinfo, int comp_index,
JDIFFROW diff_buf, JDIFFROW prev_row,
JDIFFROW undiff_buf, JDIMENSION width)
{
UNDIFFERENCE_1D(INITIAL_PREDICTOR2);
}
METHODDEF(void)
jpeg_undifference2(j_decompress_ptr cinfo, int comp_index,
JDIFFROW diff_buf, JDIFFROW prev_row,
JDIFFROW undiff_buf, JDIMENSION width)
{
UNDIFFERENCE_2D(PREDICTOR2);
}
METHODDEF(void)
jpeg_undifference3(j_decompress_ptr cinfo, int comp_index,
JDIFFROW diff_buf, JDIFFROW prev_row,
JDIFFROW undiff_buf, JDIMENSION width)
{
UNDIFFERENCE_2D(PREDICTOR3);
}
METHODDEF(void)
jpeg_undifference4(j_decompress_ptr cinfo, int comp_index,
JDIFFROW diff_buf, JDIFFROW prev_row,
JDIFFROW undiff_buf, JDIMENSION width)
{
UNDIFFERENCE_2D(PREDICTOR4);
}
METHODDEF(void)
jpeg_undifference5(j_decompress_ptr cinfo, int comp_index,
JDIFFROW diff_buf, JDIFFROW prev_row,
JDIFFROW undiff_buf, JDIMENSION width)
{
SHIFT_TEMPS
UNDIFFERENCE_2D(PREDICTOR5);
}
METHODDEF(void)
jpeg_undifference6(j_decompress_ptr cinfo, int comp_index,
JDIFFROW diff_buf, JDIFFROW prev_row,
JDIFFROW undiff_buf, JDIMENSION width)
{
SHIFT_TEMPS
UNDIFFERENCE_2D(PREDICTOR6);
}
METHODDEF(void)
jpeg_undifference6a(j_decompress_ptr cinfo, int comp_index,
JDIFFROW diff_buf, JDIFFROW prev_row,
JDIFFROW undiff_buf, JDIMENSION width)
{
SHIFT_TEMPS
UNDIFFERENCE_2D(PREDICTOR6A);
}
METHODDEF(void)
jpeg_undifference7(j_decompress_ptr cinfo, int comp_index,
JDIFFROW diff_buf, JDIFFROW prev_row,
JDIFFROW undiff_buf, JDIMENSION width)
{
SHIFT_TEMPS
UNDIFFERENCE_2D(PREDICTOR7);
}
/*
* Undifferencer for the first row in a scan or restart interval. The first
* sample in the row is undifferenced using the special predictor constant
* x=2^(P-Pt-1). The rest of the samples are undifferenced using the
* 1-D horizontal predictor (1).
*/
METHODDEF(void)
jpeg_undifference_first_row(j_decompress_ptr cinfo, int comp_index,
JDIFFROW diff_buf, JDIFFROW prev_row,
JDIFFROW undiff_buf, JDIMENSION width)
{
j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;
UNDIFFERENCE_1D(INITIAL_PREDICTORx);
/*
* Now that we have undifferenced the first row, we want to use the
* undifferencer which corresponds to the predictor specified in the
* scan header.
*/
switch (cinfo->Ss) {
case 1:
losslsd->predict_undifference[comp_index] = jpeg_undifference1;
break;
case 2:
losslsd->predict_undifference[comp_index] = jpeg_undifference2;
break;
case 3:
losslsd->predict_undifference[comp_index] = jpeg_undifference3;
break;
case 4:
losslsd->predict_undifference[comp_index] = jpeg_undifference4;
break;
case 5:
losslsd->predict_undifference[comp_index] = jpeg_undifference5;
break;
case 6:
/* DCMTK specific code that is only needed in the 16-bit library.
* Enables workaround for faulty images with integer overflow in predictor 6.
*/
if (cinfo->workaround_options & WORKAROUND_PREDICTOR6OVERFLOW)
losslsd->predict_undifference[comp_index] = jpeg_undifference6a;
else losslsd->predict_undifference[comp_index] = jpeg_undifference6;
break;
case 7:
losslsd->predict_undifference[comp_index] = jpeg_undifference7;
break;
}
}
/*
* Initialize for an input processing pass.
*/
METHODDEF(void)
predict_start_pass (j_decompress_ptr cinfo)
{
j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;
int ci;
/* Check that the scan parameters Ss, Se, Ah, Al are OK for lossless JPEG.
*
* Ss is the predictor selection value (psv). Legal values for sequential
* lossless JPEG are: 1 <= psv <= 7.
*
* Se and Ah are not used and should be zero.
*
* Al specifies the point transform (Pt). Legal values are: 0 <= Pt <= 15.
*/
if (cinfo->Ss < 1 || cinfo->Ss > 7 ||
cinfo->Se != 0 || cinfo->Ah != 0 ||
cinfo->Al > 15) /* need not check for < 0 */
ERREXIT4(cinfo, JERR_BAD_LOSSLESS,
cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
/* Set undifference functions to first row function */
for (ci = 0; ci < cinfo->num_components; ci++)
losslsd->predict_undifference[ci] = jpeg_undifference_first_row;
}
/*
* Module initialization routine for the undifferencer.
*/
GLOBAL(void)
jinit_undifferencer (j_decompress_ptr cinfo)
{
j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;
losslsd->predict_start_pass = predict_start_pass;
losslsd->predict_process_restart = predict_start_pass;
}
#endif /* D_LOSSLESS_SUPPORTED */
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