[GRASS-SVN] r43936 - grass/trunk/imagery/i.rectify

[svn_grass at osgeo.org]

Author: mmetz
Date: 2010-10-16 09:50:35 -0700 (Sat, 16 Oct 2010)
New Revision: 43936

Modified:
   grass/trunk/imagery/i.rectify/bilinear.c
   grass/trunk/imagery/i.rectify/cubic.c
   grass/trunk/imagery/i.rectify/nearest.c
Log:
fix bilinear/bicubic interpolation

Modified: grass/trunk/imagery/i.rectify/bilinear.c
===================================================================
--- grass/trunk/imagery/i.rectify/bilinear.c	2010-10-16 15:23:47 UTC (rev 43935)
+++ grass/trunk/imagery/i.rectify/bilinear.c	2010-10-16 16:50:35 UTC (rev 43936)
@@ -32,7 +32,11 @@
       result;			/* result of interpolation       */
     DCELL *c00, *c01, *c10, *c11;
 
-    /* cut indices to integer */
+    /* cut indices to integer and get nearest cells */
+    /* example: *row_idx = 2.1
+     * nearest rows are 1 and 2, not 2 and 3 */
+    *row_idx -= 0.5;
+    *col_idx -= 0.5;
     row0 = (int)floor(*row_idx);
     col0 = (int)floor(*col_idx);
     row1 = row0 + 1;

Modified: grass/trunk/imagery/i.rectify/cubic.c
===================================================================
--- grass/trunk/imagery/i.rectify/cubic.c	2010-10-16 15:23:47 UTC (rev 43935)
+++ grass/trunk/imagery/i.rectify/cubic.c	2010-10-16 16:50:35 UTC (rev 43936)
@@ -33,7 +33,14 @@
       val[4];			/* buffer for temporary values   */
     DCELL *cellp[4][4];
 
-    /* cut indices to integer */
+    /* cut indices to integer and get nearest cells */
+    /* example: *row_idx = 2.1
+     * nearest rows are 0, 1, 2 and 3, not 1, 2, 3 and 4
+     * row 0 streches from 0 to 1, row 4 from 4 to 5
+     * 2.1 - 1 = 1.1
+     * 4 - 2.1 = 1.9 */
+    *row_idx -= 0.5;
+    *col_idx -= 0.5;
     row = (int)floor(*row_idx);
     col = (int)floor(*col_idx);
 

Modified: grass/trunk/imagery/i.rectify/nearest.c
===================================================================
--- grass/trunk/imagery/i.rectify/nearest.c	2010-10-16 15:23:47 UTC (rev 43935)
+++ grass/trunk/imagery/i.rectify/nearest.c	2010-10-16 16:50:35 UTC (rev 43936)
@@ -20,7 +20,8 @@
     int row, col;		/* row/col of nearest neighbor   */
     DCELL *cellp;
 
-    /* cut indices to integer */
+    /* cut indices to integer and get nearest cell */
+    /* the row_idx, col_idx correction for bilinear/bicubic does not apply here */
     row = (int)floor(*row_idx);
     col = (int)floor(*col_idx);