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+/*
+ * jdlossls.c
+ *
+ * This file was part of the Independent JPEG Group's software:
+ * Copyright (C) 1998, Thomas G. Lane.
+ * Lossless JPEG Modifications:
+ * Copyright (C) 1999, Ken Murchison.
+ * libjpeg-turbo Modifications:
+ * Copyright (C) 2022, D. R. Commander.
+ * For conditions of distribution and use, see the accompanying README.ijg
+ * file.
+ *
+ * This file contains prediction, sample undifferencing, point transform, and
+ * sample scaling routines for the lossless JPEG decompressor.
+ */
+
+#define JPEG_INTERNALS
+#include "jinclude.h"
+#include "jpeglib.h"
+#include "jlossls.h"
+
+#ifdef D_LOSSLESS_SUPPORTED
+
+
+/**************** Sample undifferencing (reconstruction) *****************/
+
+/*
+ * In order to avoid a performance penalty for checking which predictor is
+ * being used and which row is being processed for each call of the
+ * undifferencer, and to promote optimization, we have separate undifferencing
+ * functions for each predictor selection value.
+ *
+ * We are able to avoid duplicating source code by implementing the predictors
+ * and undifferencers as macros. Each of the undifferencing functions is
+ * simply a wrapper around an UNDIFFERENCE macro with the appropriate PREDICTOR
+ * macro passed as an argument.
+ */
+
+/* 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 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) \
+ int Ra; \
+ \
+ Ra = (*diff_buf++ + INITIAL_PREDICTOR) & 0xFFFF; \
+ *undiff_buf++ = Ra; \
+ \
+ while (--width) { \
+ Ra = (*diff_buf++ + PREDICTOR1) & 0xFFFF; \
+ *undiff_buf++ = 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, and 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) \
+ int Ra, Rb, Rc; \
+ \
+ Rb = *prev_row++; \
+ Ra = (*diff_buf++ + PREDICTOR2) & 0xFFFF; \
+ *undiff_buf++ = Ra; \
+ \
+ while (--width) { \
+ Rc = Rb; \
+ Rb = *prev_row++; \
+ Ra = (*diff_buf++ + PREDICTOR) & 0xFFFF; \
+ *undiff_buf++ = Ra; \
+ }
+
+
+/*
+ * Undifferencers for the second and subsequent rows 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);
+ (void)(Rc);
+}
+
+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)
+{
+ 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)
+{
+ UNDIFFERENCE_2D(PREDICTOR6);
+}
+
+METHODDEF(void)
+jpeg_undifference7(j_decompress_ptr cinfo, int comp_index,
+ JDIFFROW diff_buf, JDIFFROW prev_row,
+ JDIFFROW undiff_buf, JDIMENSION width)
+{
+ UNDIFFERENCE_2D(PREDICTOR7);
+ (void)(Rc);
+}
+
+
+/*
+ * 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)
+{
+ lossless_decomp_ptr losslessd = (lossless_decomp_ptr)cinfo->idct;
+
+ UNDIFFERENCE_1D(INITIAL_PREDICTORx);
+
+ /*
+ * Now that we have undifferenced the first row, we want to use the
+ * undifferencer that corresponds to the predictor specified in the
+ * scan header.
+ */
+ switch (cinfo->Ss) {
+ case 1:
+ losslessd->predict_undifference[comp_index] = jpeg_undifference1;
+ break;
+ case 2:
+ losslessd->predict_undifference[comp_index] = jpeg_undifference2;
+ break;
+ case 3:
+ losslessd->predict_undifference[comp_index] = jpeg_undifference3;
+ break;
+ case 4:
+ losslessd->predict_undifference[comp_index] = jpeg_undifference4;
+ break;
+ case 5:
+ losslessd->predict_undifference[comp_index] = jpeg_undifference5;
+ break;
+ case 6:
+ losslessd->predict_undifference[comp_index] = jpeg_undifference6;
+ break;
+ case 7:
+ losslessd->predict_undifference[comp_index] = jpeg_undifference7;
+ break;
+ }
+}
+
+
+/*********************** Sample upscaling by 2^Pt ************************/
+
+METHODDEF(void)
+simple_upscale(j_decompress_ptr cinfo,
+ JDIFFROW diff_buf, _JSAMPROW output_buf, JDIMENSION width)
+{
+ do {
+ *output_buf++ = (_JSAMPLE)(*diff_buf++ << cinfo->Al);
+ } while (--width);
+}
+
+METHODDEF(void)
+noscale(j_decompress_ptr cinfo,
+ JDIFFROW diff_buf, _JSAMPROW output_buf, JDIMENSION width)
+{
+ do {
+ *output_buf++ = (_JSAMPLE)(*diff_buf++);
+ } while (--width);
+}
+
+
+/*
+ * Initialize for an input processing pass.
+ */
+
+METHODDEF(void)
+start_pass_lossless(j_decompress_ptr cinfo)
+{
+ lossless_decomp_ptr losslessd = (lossless_decomp_ptr)cinfo->idct;
+ 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 <= (data precision - 1).
+ */
+ if (cinfo->Ss < 1 || cinfo->Ss > 7 ||
+ cinfo->Se != 0 || cinfo->Ah != 0 ||
+ cinfo->Al < 0 || cinfo->Al >= cinfo->data_precision)
+ ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
+ cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
+
+ /* Set undifference functions to first row function */
+ for (ci = 0; ci < cinfo->num_components; ci++)
+ losslessd->predict_undifference[ci] = jpeg_undifference_first_row;
+
+ /* Set scaler function based on Pt */
+ if (cinfo->Al)
+ losslessd->scaler_scale = simple_upscale;
+ else
+ losslessd->scaler_scale = noscale;
+}
+
+
+/*
+ * Initialize the lossless decompressor.
+ */
+
+GLOBAL(void)
+_jinit_lossless_decompressor(j_decompress_ptr cinfo)
+{
+ lossless_decomp_ptr losslessd;
+
+ /* Create subobject in permanent pool */
+ losslessd = (lossless_decomp_ptr)
+ (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_PERMANENT,
+ sizeof(jpeg_lossless_decompressor));
+ cinfo->idct = (struct jpeg_inverse_dct *)losslessd;
+ losslessd->pub.start_pass = start_pass_lossless;
+}
+
+#endif /* D_LOSSLESS_SUPPORTED */