The Independent JPEG Group's JPEG software v3

1 files changed, 101 insertions, 14 deletions

diff --git a/jdsample.c b/jdsample.c
index 15dbf4f8..71fb4534 100644
--- a/jdsample.c
+++ b/jdsample.c
@@ -1,7 +1,7 @@
 /*
  * jdsample.c
  *
- * Copyright (C) 1991, Thomas G. Lane.
+ * Copyright (C) 1991, 1992, 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.
  *
@@ -26,30 +26,33 @@ unsubsample_init (decompress_info_ptr cinfo)
 
 /*
  * Un-subsample pixel values of a single component.
- * This version only handles integral sampling ratios.
+ * This version handles any integral sampling ratios.
+ * This is not used for typical JPEG files, so it need not be fast.
  */
 
 METHODDEF void
-unsubsample (decompress_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)
+int_unsubsample (decompress_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];
-  short h_expand, v_expand, h, v;
+  register JSAMPROW inptr, outptr;
+  register JSAMPLE invalue;
+  register short h_expand, h;
+  short v_expand, v;
   int inrow, outrow;
-  long incol;
-  JSAMPROW inptr, outptr;
-  JSAMPLE invalue;
+  register long incol;
 
-  /* TEMP FOR DEBUGGING PIPELINE CONTROLLER */
+#ifdef DEBUG			/* for debugging pipeline controller */
   if (input_rows != compptr->v_samp_factor ||
       output_rows != cinfo->max_v_samp_factor ||
       (input_cols % compptr->h_samp_factor) != 0 ||
       (output_cols % cinfo->max_h_samp_factor) != 0 ||
       output_cols*compptr->h_samp_factor != input_cols*cinfo->max_h_samp_factor)
     ERREXIT(cinfo->emethods, "Bogus unsubsample parameters");
+#endif
 
   h_expand = cinfo->max_h_samp_factor / compptr->h_samp_factor;
   v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
@@ -72,6 +75,85 @@ unsubsample (decompress_info_ptr cinfo, int which_component,
 
 /*
  * Un-subsample pixel values of a single component.
+ * This version handles the extremely common case of
+ * horizontal expansion by 2 and any integral vertical expansion.
+ */
+
+METHODDEF void
+h2_unsubsample (decompress_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];
+  register JSAMPROW inptr, outptr;
+  register JSAMPLE invalue;
+  short v_expand, v;
+  int inrow, outrow;
+  register long incol;
+
+#ifdef DEBUG			/* for debugging pipeline controller */
+  if (input_rows != compptr->v_samp_factor ||
+      output_rows != cinfo->max_v_samp_factor ||
+      (input_cols % compptr->h_samp_factor) != 0 ||
+      (output_cols % cinfo->max_h_samp_factor) != 0 ||
+      output_cols*compptr->h_samp_factor != input_cols*cinfo->max_h_samp_factor)
+    ERREXIT(cinfo->emethods, "Bogus unsubsample parameters");
+#endif
+
+  v_expand = cinfo->max_v_samp_factor / compptr->v_samp_factor;
+
+/* The subsampled image width will always be a multiple of DCTSIZE,
+ * so we can unroll the inner loop.
+ */
+
+  outrow = 0;
+  for (inrow = 0; inrow < input_rows; inrow++) {
+    for (v = 0; v < v_expand; v++) {
+      inptr = input_data[inrow];
+      outptr = output_data[outrow++];
+#if DCTSIZE == 8
+      for (incol = 0; incol < input_cols; incol += DCTSIZE) {
+	invalue = GETJSAMPLE(*inptr++);
+	*outptr++ = invalue;
+	*outptr++ = invalue;
+	invalue = GETJSAMPLE(*inptr++);
+	*outptr++ = invalue;
+	*outptr++ = invalue;
+	invalue = GETJSAMPLE(*inptr++);
+	*outptr++ = invalue;
+	*outptr++ = invalue;
+	invalue = GETJSAMPLE(*inptr++);
+	*outptr++ = invalue;
+	*outptr++ = invalue;
+	invalue = GETJSAMPLE(*inptr++);
+	*outptr++ = invalue;
+	*outptr++ = invalue;
+	invalue = GETJSAMPLE(*inptr++);
+	*outptr++ = invalue;
+	*outptr++ = invalue;
+	invalue = GETJSAMPLE(*inptr++);
+	*outptr++ = invalue;
+	*outptr++ = invalue;
+	invalue = GETJSAMPLE(*inptr++);
+	*outptr++ = invalue;
+	*outptr++ = invalue;
+      }
+#else /* nonstandard DCTSIZE */
+      for (incol = 0; incol < input_cols; incol++) {
+	invalue = GETJSAMPLE(*inptr++);
+	*outptr++ = invalue;
+	*outptr++ = invalue;
+      }
+#endif
+    }
+  }
+}
+
+
+/*
+ * Un-subsample pixel values of a single component.
  * This version handles the special case of a full-size component.
  */
 
@@ -82,8 +164,10 @@ fullsize_unsubsample (decompress_info_ptr cinfo, int which_component,
 		      JSAMPARRAY above, JSAMPARRAY input_data, JSAMPARRAY below,
 		      JSAMPARRAY output_data)
 {
-  if (input_cols != output_cols || input_rows != output_rows) /* DEBUG */
+#ifdef DEBUG			/* for debugging pipeline controller */
+  if (input_cols != output_cols || input_rows != output_rows)
     ERREXIT(cinfo->emethods, "Pipeline controller messed up");
+#endif
 
   jcopy_sample_rows(input_data, 0, output_data, 0, output_rows, output_cols);
 }
@@ -121,9 +205,12 @@ jselunsubsample (decompress_info_ptr cinfo)
     if (compptr->h_samp_factor == cinfo->max_h_samp_factor &&
 	compptr->v_samp_factor == cinfo->max_v_samp_factor)
       cinfo->methods->unsubsample[ci] = fullsize_unsubsample;
+    else if (compptr->h_samp_factor * 2 == cinfo->max_h_samp_factor &&
+	     (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0)
+      cinfo->methods->unsubsample[ci] = h2_unsubsample;
     else if ((cinfo->max_h_samp_factor % compptr->h_samp_factor) == 0 &&
 	     (cinfo->max_v_samp_factor % compptr->v_samp_factor) == 0)
-      cinfo->methods->unsubsample[ci] = unsubsample;
+      cinfo->methods->unsubsample[ci] = int_unsubsample;
     else
       ERREXIT(cinfo->emethods, "Fractional subsampling not implemented yet");
   }