Index: trunk/pswarp/src/pswarpTransformTile.c
===================================================================
--- trunk/pswarp/src/pswarpTransformTile.c	(revision 19136)
+++ trunk/pswarp/src/pswarpTransformTile.c	(revision 19149)
@@ -87,5 +87,5 @@
 
             // psImagePixelInterpolate determines the value at pixel coordinate (x,y) in child coordinates
-            maskValue = inMaskData ? inMaskData[(int)round(yIn)][(int)round(xIn)] : 0;
+            maskValue = inMaskData ? inMaskData[(int)yIn][(int)xIn] : 0;
             if (!psImageInterpolate(&imageValue, &varValue, &maskValue, xIn, yIn, args->interp)) {
                 psError(PS_ERR_UNKNOWN, false, "Unable to interpolate image.");