IJG's JPEG software v6b with lossless JPEG support

Patch obtained from:
https://sourceforge.net/projects/jpeg/files/ftp.oceana.com

Author date taken from original announcement and timestamp of patch
tarball:
https://groups.google.com/g/comp.protocols.dicom/c/rrkP8BxoMRk/m/Ij4dfprggp8J

jdlossls.c

@@ -0,0 +1,94 @@
+/*
+ * jdlossls.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 the control logic for the lossless JPEG decompressor.
+ */
+
+#define JPEG_INTERNALS
+#include "jinclude.h"
+#include "jpeglib.h"
+#include "jlossls.h"
+
+
+#ifdef D_LOSSLESS_SUPPORTED
+
+/*
+ * Compute output image dimensions and related values.
+ */
+
+METHODDEF(void)
+calc_output_dimensions (j_decompress_ptr cinfo)
+{
+  /* Hardwire it to "no scaling" */
+  cinfo->output_width = cinfo->image_width;
+  cinfo->output_height = cinfo->image_height;
+  /* jdinput.c has already initialized codec_data_unit to 1,
+   * and has computed unscaled downsampled_width and downsampled_height.
+   */
+}
+
+
+/*
+ * Initialize for an input processing pass.
+ */
+
+METHODDEF(void)
+start_input_pass (j_decompress_ptr cinfo)
+{
+  j_lossless_d_ptr losslsd = (j_lossless_d_ptr) cinfo->codec;
+
+  (*losslsd->entropy_start_pass) (cinfo);
+  (*losslsd->predict_start_pass) (cinfo);
+  (*losslsd->scaler_start_pass) (cinfo);
+  (*losslsd->diff_start_input_pass) (cinfo);
+}
+
+
+/*
+ * Initialize the lossless decompression codec.
+ * This is called only once, during master selection.
+ */
+
+GLOBAL(void) 
+jinit_lossless_d_codec(j_decompress_ptr cinfo)
+{
+  j_lossless_d_ptr losslsd;
+  boolean use_c_buffer;
+
+  /* Create subobject in permanent pool */
+  losslsd = (j_lossless_d_ptr)
+    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
+				SIZEOF(jpeg_lossless_d_codec));
+  cinfo->codec = (struct jpeg_d_codec *) losslsd;
+
+  /* Initialize sub-modules */
+  /* Entropy decoding: either Huffman or arithmetic coding. */
+  if (cinfo->arith_code) {
+    ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
+  } else {
+    jinit_lhuff_decoder(cinfo);
+  }
+
+  /* Undifferencer */
+  jinit_undifferencer(cinfo);
+
+  /* Scaler */
+  jinit_d_scaler(cinfo);
+
+  use_c_buffer = cinfo->inputctl->has_multiple_scans || cinfo->buffered_image;
+  jinit_d_diff_controller(cinfo, use_c_buffer);
+
+  /* Initialize method pointers.
+   *
+   * Note: consume_data, start_output_pass and decompress_data are
+   * assigned in jddiffct.c.
+   */
+  losslsd->pub.calc_output_dimensions = calc_output_dimensions;
+  losslsd->pub.start_input_pass = start_input_pass;
+}
+
+#endif /* D_LOSSLESS_SUPPORTED */