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/*
* jcpred.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 differencing 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 differencing
* functions for each case.
*
* We are able to avoid duplicating source code by implementing the predictors
* and differencers as macros. Each of the differencing functions are
* simply wrappers around a DIFFERENCE macro with the appropriate PREDICTOR
* macro passed as an argument.
*/
#define JPEG_INTERNALS
#include "jinclude12.h"
#include "jpeglib12.h"
#include "jlossls12.h" /* Private declarations for lossless codec */
#ifdef C_LOSSLESS_SUPPORTED
/* Private predictor object */
typedef struct {
/* MCU-rows left in the restart interval for each component */
unsigned int restart_rows_to_go[MAX_COMPONENTS];
} c_predictor;
typedef c_predictor * c_pred_ptr;
/* Forward declarations */
LOCAL(void) reset_predictor
JPP((j_compress_ptr cinfo, int ci));
METHODDEF(void) start_pass
JPP((j_compress_ptr cinfo));
/* 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 differencer 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.
*/
#define DIFFERENCE_1D(INITIAL_PREDICTOR) \
j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec; \
c_pred_ptr pred = (c_pred_ptr) losslsc->pred_private; \
boolean restart = FALSE; \
unsigned int xindex; \
int samp, Ra; \
\
samp = GETJSAMPLE(input_buf[0]); \
diff_buf[0] = samp - INITIAL_PREDICTOR; \
\
for (xindex = 1; xindex < width; xindex++) { \
Ra = samp; \
samp = GETJSAMPLE(input_buf[xindex]); \
diff_buf[xindex] = samp - PREDICTOR1; \
} \
\
/* Account for restart interval (no-op if not using restarts) */ \
if (cinfo->restart_interval) { \
if (--(pred->restart_rows_to_go[ci]) == 0) { \
reset_predictor(cinfo, ci); \
restart = TRUE; \
} \
}
/*
* 2-Dimensional differencer 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.
*/
#define DIFFERENCE_2D(PREDICTOR) \
j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec; \
c_pred_ptr pred = (c_pred_ptr) losslsc->pred_private; \
unsigned int xindex; \
int samp, Ra, Rb, Rc; \
\
Rb = GETJSAMPLE(prev_row[0]); \
samp = GETJSAMPLE(input_buf[0]); \
diff_buf[0] = samp - PREDICTOR2; \
\
for (xindex = 1; xindex < width; xindex++) { \
Rc = Rb; \
Rb = GETJSAMPLE(prev_row[xindex]); \
Ra = samp; \
samp = GETJSAMPLE(input_buf[xindex]); \
diff_buf[xindex] = samp - PREDICTOR; \
} \
\
/* Account for restart interval (no-op if not using restarts) */ \
if (cinfo->restart_interval) { \
if (--pred->restart_rows_to_go[ci] == 0) \
reset_predictor(cinfo, ci); \
}
/*
* Differencers for the all rows but the first in a scan or restart interval.
* The first sample in the row is differenced using the vertical
* predictor (2). The rest of the samples are differenced using the
* predictor specified in the scan header.
*/
METHODDEF(void)
jpeg_difference1(j_compress_ptr cinfo, int ci,
JSAMPROW input_buf, JSAMPROW prev_row,
JDIFFROW diff_buf, JDIMENSION width)
{
DIFFERENCE_1D(INITIAL_PREDICTOR2);
}
METHODDEF(void)
jpeg_difference2(j_compress_ptr cinfo, int ci,
JSAMPROW input_buf, JSAMPROW prev_row,
JDIFFROW diff_buf, JDIMENSION width)
{
DIFFERENCE_2D(PREDICTOR2);
}
METHODDEF(void)
jpeg_difference3(j_compress_ptr cinfo, int ci,
JSAMPROW input_buf, JSAMPROW prev_row,
JDIFFROW diff_buf, JDIMENSION width)
{
DIFFERENCE_2D(PREDICTOR3);
}
METHODDEF(void)
jpeg_difference4(j_compress_ptr cinfo, int ci,
JSAMPROW input_buf, JSAMPROW prev_row,
JDIFFROW diff_buf, JDIMENSION width)
{
DIFFERENCE_2D(PREDICTOR4);
}
METHODDEF(void)
jpeg_difference5(j_compress_ptr cinfo, int ci,
JSAMPROW input_buf, JSAMPROW prev_row,
JDIFFROW diff_buf, JDIMENSION width)
{
SHIFT_TEMPS
DIFFERENCE_2D(PREDICTOR5);
}
METHODDEF(void)
jpeg_difference6(j_compress_ptr cinfo, int ci,
JSAMPROW input_buf, JSAMPROW prev_row,
JDIFFROW diff_buf, JDIMENSION width)
{
SHIFT_TEMPS
DIFFERENCE_2D(PREDICTOR6);
}
METHODDEF(void)
jpeg_difference7(j_compress_ptr cinfo, int ci,
JSAMPROW input_buf, JSAMPROW prev_row,
JDIFFROW diff_buf, JDIMENSION width)
{
SHIFT_TEMPS
DIFFERENCE_2D(PREDICTOR7);
}
/*
* Differencer for the first row in a scan or restart interval. The first
* sample in the row is differenced using the special predictor constant
* x=2^(P-Pt-1). The rest of the samples are differenced using the
* 1-D horizontal predictor (1).
*/
METHODDEF(void)
jpeg_difference_first_row(j_compress_ptr cinfo, int ci,
JSAMPROW input_buf, JSAMPROW prev_row,
JDIFFROW diff_buf, JDIMENSION width)
{
DIFFERENCE_1D(INITIAL_PREDICTORx);
/*
* Now that we have differenced the first row, we want to use the
* differencer which corresponds to the predictor specified in the
* scan header.
*
* Note that we don't to do this if we have just reset the predictor
* for a new restart interval.
*/
if (!restart) {
switch (cinfo->Ss) {
case 1:
losslsc->predict_difference[ci] = jpeg_difference1;
break;
case 2:
losslsc->predict_difference[ci] = jpeg_difference2;
break;
case 3:
losslsc->predict_difference[ci] = jpeg_difference3;
break;
case 4:
losslsc->predict_difference[ci] = jpeg_difference4;
break;
case 5:
losslsc->predict_difference[ci] = jpeg_difference5;
break;
case 6:
losslsc->predict_difference[ci] = jpeg_difference6;
break;
case 7:
losslsc->predict_difference[ci] = jpeg_difference7;
break;
}
}
}
/*
* Reset predictor at the start of a pass or restart interval.
*/
LOCAL(void)
reset_predictor (j_compress_ptr cinfo, int ci)
{
j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;
c_pred_ptr pred = (c_pred_ptr) losslsc->pred_private;
/* Initialize restart counter */
pred->restart_rows_to_go[ci] =
cinfo->restart_interval / cinfo->MCUs_per_row;
/* Set difference function to first row function */
losslsc->predict_difference[ci] = jpeg_difference_first_row;
}
/*
* Initialize for an input processing pass.
*/
METHODDEF(void)
start_pass (j_compress_ptr cinfo)
{
/* j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec; */
/* c_pred_ptr pred = (c_pred_ptr) losslsc->pred_private; */
int ci;
/* Check that the restart interval is an integer multiple of the number
* of MCU in an MCU-row.
*/
if (cinfo->restart_interval % cinfo->MCUs_per_row != 0)
ERREXIT2(cinfo, JERR_BAD_RESTART,
cinfo->restart_interval, cinfo->MCUs_per_row);
/* Set predictors for start of pass */
for (ci = 0; ci < cinfo->num_components; ci++)
reset_predictor(cinfo, ci);
}
/*
* Module initialization routine for the differencer.
*/
GLOBAL(void)
jinit_differencer (j_compress_ptr cinfo)
{
j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;
c_pred_ptr pred;
pred = (c_pred_ptr)
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
SIZEOF(c_predictor));
losslsc->pred_private = (void *) pred;
losslsc->predict_start_pass = start_pass;
}
#endif /* C_LOSSLESS_SUPPORTED */
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