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jdlossls.c
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287
jdlossls.c
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/*
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* jdlossls.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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* libjpeg-turbo Modifications:
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* Copyright (C) 2022, D. R. Commander.
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* For conditions of distribution and use, see the accompanying README.ijg
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* file.
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*
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* This file contains prediction, sample undifferencing, point transform, and
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* sample scaling routines for the lossless JPEG decompressor.
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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"
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#ifdef D_LOSSLESS_SUPPORTED
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/**************** Sample undifferencing (reconstruction) *****************/
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/*
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* In order to avoid a performance penalty for checking which predictor is
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* being used and which row is 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 predictor selection value.
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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 is
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* simply a wrapper 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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/* 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 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 Ra; \
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\
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Ra = (*diff_buf++ + INITIAL_PREDICTOR) & 0xFFFF; \
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*undiff_buf++ = Ra; \
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\
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while (--width) { \
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Ra = (*diff_buf++ + PREDICTOR1) & 0xFFFF; \
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*undiff_buf++ = 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, and 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 Ra, Rb, Rc; \
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\
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Rb = *prev_row++; \
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Ra = (*diff_buf++ + PREDICTOR2) & 0xFFFF; \
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*undiff_buf++ = Ra; \
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\
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while (--width) { \
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Rc = Rb; \
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Rb = *prev_row++; \
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Ra = (*diff_buf++ + PREDICTOR) & 0xFFFF; \
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*undiff_buf++ = Ra; \
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}
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/*
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* Undifferencers for the second and subsequent rows in a scan or restart
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* interval. 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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(void)(Rc);
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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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(void)(Rc);
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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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lossless_decomp_ptr losslessd = (lossless_decomp_ptr)cinfo->idct;
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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 that 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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losslessd->predict_undifference[comp_index] = jpeg_undifference1;
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break;
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case 2:
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losslessd->predict_undifference[comp_index] = jpeg_undifference2;
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break;
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case 3:
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losslessd->predict_undifference[comp_index] = jpeg_undifference3;
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break;
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case 4:
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losslessd->predict_undifference[comp_index] = jpeg_undifference4;
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break;
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case 5:
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losslessd->predict_undifference[comp_index] = jpeg_undifference5;
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break;
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case 6:
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losslessd->predict_undifference[comp_index] = jpeg_undifference6;
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break;
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case 7:
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losslessd->predict_undifference[comp_index] = jpeg_undifference7;
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break;
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}
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}
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/*********************** Sample upscaling by 2^Pt ************************/
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METHODDEF(void)
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simple_upscale(j_decompress_ptr cinfo,
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JDIFFROW diff_buf, _JSAMPROW output_buf, JDIMENSION width)
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{
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while (width--)
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*output_buf++ = (_JSAMPLE)(*diff_buf++ << cinfo->Al);
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}
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METHODDEF(void)
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noscale(j_decompress_ptr cinfo,
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JDIFFROW diff_buf, _JSAMPROW output_buf, JDIMENSION width)
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{
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while (width--)
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*output_buf++ = (_JSAMPLE)(*diff_buf++);
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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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start_pass_lossless(j_decompress_ptr cinfo)
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{
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lossless_decomp_ptr losslessd = (lossless_decomp_ptr)cinfo->idct;
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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).
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* Legal values are: 0 <= Pt <= (data precision - 1).
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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 < 0 || cinfo->Al >= cinfo->data_precision)
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ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
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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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losslessd->predict_undifference[ci] = jpeg_undifference_first_row;
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/* Set scaler function based on Pt */
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if (cinfo->Al)
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losslessd->scaler_scale = simple_upscale;
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else
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losslessd->scaler_scale = noscale;
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}
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/*
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* Initialize the lossless decompressor.
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*/
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GLOBAL(void)
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_jinit_lossless_decompressor(j_decompress_ptr cinfo)
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{
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lossless_decomp_ptr losslessd;
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/* Create subobject in permanent pool */
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losslessd = (lossless_decomp_ptr)
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(*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_PERMANENT,
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sizeof(jpeg_lossless_decompressor));
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cinfo->idct = (struct jpeg_inverse_dct *)losslessd;
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losslessd->pub.start_pass = start_pass_lossless;
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}
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#endif /* D_LOSSLESS_SUPPORTED */
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Reference in New Issue
Block a user