ec6e451d05
Referring to https://github.com/libjpeg-turbo/libjpeg-turbo/issues/402#issuecomment-768348440 and https://github.com/libjpeg-turbo/libjpeg-turbo/issues/402#issuecomment-770221584 Ken Murchison clarified that it was his intent to release the lossless JPEG patch under the IJG License and that adding his name to the copyright headers would be sufficient to acknowledge that any derivatives are based on his work.
250 lines
7.1 KiB
C
250 lines
7.1 KiB
C
/*
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* jdpred.c
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*
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* This file was part of the Independent JPEG Group's software:
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* Copyright (C) 1998, Thomas G. Lane.
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* Lossless JPEG Modifications:
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* Copyright (C) 1999, Ken Murchison.
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* For conditions of distribution and use, see the accompanying README file.
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*
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* This file contains sample undifferencing (reconstruction) for lossless JPEG.
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*
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* In order to avoid paying the performance penalty of having to check the
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* predictor being used and the row being processed for each call of the
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* undifferencer, and to promote optimization, we have separate undifferencing
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* functions for each case.
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*
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* We are able to avoid duplicating source code by implementing the predictors
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* and undifferencers as macros. Each of the undifferencing functions are
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* simply wrappers around an UNDIFFERENCE macro with the appropriate PREDICTOR
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* macro passed as an argument.
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*/
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#define JPEG_INTERNALS
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#include "jinclude.h"
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#include "jpeglib.h"
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#include "jlossls.h" /* Private declarations for lossless codec */
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#ifdef D_LOSSLESS_SUPPORTED
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/* Predictor for the first column of the first row: 2^(P-Pt-1) */
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#define INITIAL_PREDICTORx (1 << (cinfo->data_precision - cinfo->Al - 1))
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/* Predictor for the first column of the remaining rows: Rb */
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#define INITIAL_PREDICTOR2 GETJSAMPLE(prev_row[0])
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/*
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* 1-Dimensional undifferencer routine.
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*
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* This macro implements the 1-D horizontal predictor (1). INITIAL_PREDICTOR
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* is used as the special case predictor for the first column, which must be
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* either INITIAL_PREDICTOR2 or INITIAL_PREDICTORx. The remaining samples
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* use PREDICTOR1.
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*
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* The reconstructed sample is supposed to be calculated modulo 2^16, so we
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* logically AND the result with 0xFFFF.
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*/
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#define UNDIFFERENCE_1D(INITIAL_PREDICTOR) \
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int xindex; \
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int Ra; \
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\
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Ra = (diff_buf[0] + INITIAL_PREDICTOR) & 0xFFFF; \
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undiff_buf[0] = Ra; \
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\
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for (xindex = 1; xindex < width; xindex++) { \
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Ra = (diff_buf[xindex] + PREDICTOR1) & 0xFFFF; \
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undiff_buf[xindex] = Ra; \
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}
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/*
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* 2-Dimensional undifferencer routine.
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*
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* This macro implements the 2-D horizontal predictors (#2-7). PREDICTOR2 is
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* used as the special case predictor for the first column. The remaining
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* samples use PREDICTOR, which is a function of Ra, Rb, Rc.
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*
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* Because prev_row and output_buf may point to the same storage area (in an
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* interleaved image with Vi=1, for example), we must take care to buffer Rb/Rc
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* before writing the current reconstructed sample value into output_buf.
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*
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* The reconstructed sample is supposed to be calculated modulo 2^16, so we
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* logically AND the result with 0xFFFF.
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*/
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#define UNDIFFERENCE_2D(PREDICTOR) \
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int xindex; \
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int Ra, Rb, Rc; \
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\
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Rb = GETJSAMPLE(prev_row[0]); \
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Ra = (diff_buf[0] + PREDICTOR2) & 0xFFFF; \
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undiff_buf[0] = Ra; \
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\
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for (xindex = 1; xindex < width; xindex++) { \
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Rc = Rb; \
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Rb = GETJSAMPLE(prev_row[xindex]); \
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Ra = (diff_buf[xindex] + PREDICTOR) & 0xFFFF; \
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undiff_buf[xindex] = Ra; \
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}
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/*
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* Undifferencers for the all rows but the first in a scan or restart interval.
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* The first sample in the row is undifferenced using the vertical
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* predictor (2). The rest of the samples are undifferenced using the
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* predictor specified in the scan header.
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*/
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METHODDEF(void)
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jpeg_undifference1(j_decompress_ptr cinfo, int comp_index,
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JDIFFROW diff_buf, JDIFFROW prev_row,
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JDIFFROW undiff_buf, JDIMENSION width)
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{
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UNDIFFERENCE_1D(INITIAL_PREDICTOR2);
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}
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METHODDEF(void)
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jpeg_undifference2(j_decompress_ptr cinfo, int comp_index,
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JDIFFROW diff_buf, JDIFFROW prev_row,
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JDIFFROW undiff_buf, JDIMENSION width)
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{
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UNDIFFERENCE_2D(PREDICTOR2);
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}
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METHODDEF(void)
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jpeg_undifference3(j_decompress_ptr cinfo, int comp_index,
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JDIFFROW diff_buf, JDIFFROW prev_row,
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JDIFFROW undiff_buf, JDIMENSION width)
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{
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UNDIFFERENCE_2D(PREDICTOR3);
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}
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METHODDEF(void)
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jpeg_undifference4(j_decompress_ptr cinfo, int comp_index,
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JDIFFROW diff_buf, JDIFFROW prev_row,
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JDIFFROW undiff_buf, JDIMENSION width)
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{
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UNDIFFERENCE_2D(PREDICTOR4);
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}
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METHODDEF(void)
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jpeg_undifference5(j_decompress_ptr cinfo, int comp_index,
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JDIFFROW diff_buf, JDIFFROW prev_row,
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JDIFFROW undiff_buf, JDIMENSION width)
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{
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UNDIFFERENCE_2D(PREDICTOR5);
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}
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METHODDEF(void)
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jpeg_undifference6(j_decompress_ptr cinfo, int comp_index,
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JDIFFROW diff_buf, JDIFFROW prev_row,
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JDIFFROW undiff_buf, JDIMENSION width)
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{
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UNDIFFERENCE_2D(PREDICTOR6);
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}
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METHODDEF(void)
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jpeg_undifference7(j_decompress_ptr cinfo, int comp_index,
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JDIFFROW diff_buf, JDIFFROW prev_row,
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JDIFFROW undiff_buf, JDIMENSION width)
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{
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UNDIFFERENCE_2D(PREDICTOR7);
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}
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/*
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* Undifferencer for the first row in a scan or restart interval. The first
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* sample in the row is undifferenced using the special predictor constant
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* x=2^(P-Pt-1). The rest of the samples are undifferenced using the
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* 1-D horizontal predictor (1).
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*/
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METHODDEF(void)
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jpeg_undifference_first_row(j_decompress_ptr cinfo, int comp_index,
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JDIFFROW diff_buf, JDIFFROW prev_row,
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JDIFFROW undiff_buf, JDIMENSION width)
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{
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j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;
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UNDIFFERENCE_1D(INITIAL_PREDICTORx);
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/*
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* Now that we have undifferenced the first row, we want to use the
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* undifferencer which corresponds to the predictor specified in the
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* scan header.
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*/
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switch (cinfo->Ss) {
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case 1:
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losslsd->predict_undifference[comp_index] = jpeg_undifference1;
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break;
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case 2:
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losslsd->predict_undifference[comp_index] = jpeg_undifference2;
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break;
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case 3:
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losslsd->predict_undifference[comp_index] = jpeg_undifference3;
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break;
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case 4:
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losslsd->predict_undifference[comp_index] = jpeg_undifference4;
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break;
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case 5:
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losslsd->predict_undifference[comp_index] = jpeg_undifference5;
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break;
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case 6:
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losslsd->predict_undifference[comp_index] = jpeg_undifference6;
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break;
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case 7:
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losslsd->predict_undifference[comp_index] = jpeg_undifference7;
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break;
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}
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}
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/*
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* Initialize for an input processing pass.
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*/
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METHODDEF(void)
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predict_start_pass (j_decompress_ptr cinfo)
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{
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j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;
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int ci;
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/* Check that the scan parameters Ss, Se, Ah, Al are OK for lossless JPEG.
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*
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* Ss is the predictor selection value (psv). Legal values for sequential
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* lossless JPEG are: 1 <= psv <= 7.
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*
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* Se and Ah are not used and should be zero.
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*
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* Al specifies the point transform (Pt). Legal values are: 0 <= Pt <= 15.
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*/
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if (cinfo->Ss < 1 || cinfo->Ss > 7 ||
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cinfo->Se != 0 || cinfo->Ah != 0 ||
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cinfo->Al > 15) /* need not check for < 0 */
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ERREXIT4(cinfo, JERR_BAD_LOSSLESS,
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cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
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/* Set undifference functions to first row function */
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for (ci = 0; ci < cinfo->num_components; ci++)
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losslsd->predict_undifference[ci] = jpeg_undifference_first_row;
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}
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/*
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* Module initialization routine for the undifferencer.
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*/
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GLOBAL(void)
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jinit_undifferencer (j_decompress_ptr cinfo)
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{
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j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;
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losslsd->predict_start_pass = predict_start_pass;
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losslsd->predict_process_restart = predict_start_pass;
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}
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#endif /* D_LOSSLESS_SUPPORTED */
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