The Independent JPEG Group's JPEG software v1

1 files changed, 135 insertions, 0 deletions

diff --git a/jcsample.c b/jcsample.c
new file mode 100644
index 0000000..d23e23a
--- /dev/null
+++ b/jcsample.c
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+/*
+ * jcsample.c
+ *
+ * Copyright (C) 1991, 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 subsampling routines.
+ * These routines are invoked via the subsample and
+ * subsample_init/term methods.
+ */
+
+#include "jinclude.h"
+
+
+/*
+ * Initialize for subsampling a scan.
+ */
+
+METHODDEF void
+subsample_init (compress_info_ptr cinfo)
+{
+  /* no work for now */
+}
+
+
+/*
+ * Subsample pixel values of a single component.
+ * This version only handles integral sampling ratios.
+ */
+
+METHODDEF void
+subsample (compress_info_ptr cinfo, int which_component,
+	   long input_cols, int input_rows,
+	   long output_cols, int output_rows,
+	   JSAMPARRAY above, JSAMPARRAY input_data, JSAMPARRAY below,
+	   JSAMPARRAY output_data)
+{
+  jpeg_component_info * compptr = cinfo->cur_comp_info[which_component];
+  int inrow, outrow, h_expand, v_expand, numpix, numpix2, h, v;
+  long outcol;
+  JSAMPROW inptr, outptr;
+  INT32 outvalue;
+
+  /* TEMP FOR DEBUGGING PIPELINE CONTROLLER */
+  if (output_rows != compptr->v_samp_factor ||
+      input_rows != cinfo->max_v_samp_factor ||
+      (output_cols % compptr->h_samp_factor) != 0 ||
+      (input_cols % cinfo->max_h_samp_factor) != 0 ||
+      input_cols*compptr->h_samp_factor != output_cols*cinfo->max_h_samp_factor)
+    ERREXIT(cinfo->emethods, "Bogus subsample parameters");
+
+  h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;
+  v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
+  numpix = h_expand * v_expand;
+  numpix2 = numpix/2;
+
+  inrow = 0;
+  for (outrow = 0; outrow < output_rows; outrow++) {
+    outptr = output_data[outrow];
+    for (outcol = 0; outcol < output_cols; outcol++) {
+      outvalue = 0;
+      for (v = 0; v < v_expand; v++) {
+	inptr = input_data[inrow+v] + (outcol*h_expand);
+	for (h = 0; h < h_expand; h++) {
+	  outvalue += GETJSAMPLE(*inptr++);
+	}
+      }
+      *outptr++ = (outvalue + numpix2) / numpix;
+    }
+    inrow += v_expand;
+  }
+}
+
+
+/*
+ * Subsample pixel values of a single component.
+ * This version handles the special case of a full-size component.
+ */
+
+METHODDEF void
+fullsize_subsample (compress_info_ptr cinfo, int which_component,
+		    long input_cols, int input_rows,
+		    long output_cols, int output_rows,
+		    JSAMPARRAY above, JSAMPARRAY input_data, JSAMPARRAY below,
+		    JSAMPARRAY output_data)
+{
+  if (input_cols != output_cols || input_rows != output_rows) /* DEBUG */
+    ERREXIT(cinfo->emethods, "Pipeline controller messed up");
+
+  jcopy_sample_rows(input_data, 0, output_data, 0, output_rows, output_cols);
+}
+
+
+/*
+ * Clean up after a scan.
+ */
+
+METHODDEF void
+subsample_term (compress_info_ptr cinfo)
+{
+  /* no work for now */
+}
+
+
+
+/*
+ * The method selection routine for subsampling.
+ * Note that we must select a routine for each component.
+ */
+
+GLOBAL void
+jselsubsample (compress_info_ptr cinfo)
+{
+  short ci;
+  jpeg_component_info * compptr;
+
+  if (cinfo->CCIR601_sampling)
+    ERREXIT(cinfo->emethods, "CCIR601 subsampling not implemented yet");
+
+  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
+    compptr = cinfo->cur_comp_info[ci];
+    if (compptr->h_samp_factor == cinfo->max_h_samp_factor &&
+	compptr->v_samp_factor == cinfo->max_v_samp_factor)
+      cinfo->methods->subsample[ci] = fullsize_subsample;
+    else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&
+	     (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0)
+      cinfo->methods->subsample[ci] = subsample;
+    else
+      ERREXIT(cinfo->emethods, "Fractional subsampling not implemented yet");
+  }
+
+  cinfo->methods->subsample_init = subsample_init;
+  cinfo->methods->subsample_term = subsample_term;
+}