The Independent JPEG Group's JPEG software v1

jcexpand.c

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+/*
+ * jcexpand.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 image edge-expansion routines.
+ * These routines are invoked via the edge_expand method.
+ */
+
+#include "jinclude.h"
+
+
+/*
+ * Expand an image so that it is a multiple of the MCU dimensions.
+ * This is to be accomplished by duplicating the rightmost column
+ * and/or bottommost row of pixels.  The image has not yet been
+ * subsampled, so all components have the same dimensions.
+ */
+
+METHODDEF void
+edge_expand (compress_info_ptr cinfo,
+	     long input_cols, int input_rows,
+	     long output_cols, int output_rows,
+	     JSAMPIMAGE image_data)
+{
+  /* Expand horizontally */
+  if (input_cols < output_cols) {
+    register JSAMPROW ptr;
+    register JSAMPLE pixval;
+    register long count;
+    register int row;
+    short ci;
+    long numcols = output_cols - input_cols;
+
+    for (ci = 0; ci < cinfo->num_components; ci++) {
+      for (row = 0; row < input_rows; row++) {
+	ptr = image_data[ci][row] + (input_cols-1);
+	pixval = GETJSAMPLE(*ptr++);
+	for (count = numcols; count > 0; count--)
+	  *ptr++ = pixval;
+      }
+    }
+  }
+
+  /* Expand vertically */
+  /* This happens only once at the bottom of the image, */
+  /* so it needn't be super-efficient */
+  if (input_rows < output_rows) {
+    register int row;
+    short ci;
+    JSAMPARRAY this_component;
+
+    for (ci = 0; ci < cinfo->num_components; ci++) {
+      this_component = image_data[ci];
+      for (row = input_rows; row < output_rows; row++) {
+	jcopy_sample_rows(this_component, input_rows-1, this_component, row,
+			  1, output_cols);
+      }
+    }
+  }
+}
+
+
+/*
+ * The method selection routine for edge expansion.
+ */
+
+GLOBAL void
+jselexpand (compress_info_ptr cinfo)
+{
+  /* just one implementation for now */
+  cinfo->methods->edge_expand = edge_expand;
+}