Index: trunk/psphot/src/psphotImageBackground.c
===================================================================
--- trunk/psphot/src/psphotImageBackground.c	(revision 6056)
+++ trunk/psphot/src/psphotImageBackground.c	(revision 6311)
@@ -28,6 +28,6 @@
 	double frnd = psRandomUniform (rnd);
 	int pixel = Npixels * frnd;
-	int ix = pixel / image->numCols;
-	int iy = pixel % image->numCols;
+	int ix = pixel % image->numCols;
+	int iy = pixel / image->numCols;
 	float value = image->data.F32[iy][ix];
 	if (fabs(value - Sky) > dSky) continue;