[gegl] ripple: fix x-distance from origin

[Simon Budig <simon src gnome org>]

commit 4796a58beb806665311fe4270ff04e03a193d426
Author: Simon Budig <simon budig de>
Date:   Mon Apr 23 04:08:00 2018 +0200

    ripple: fix x-distance from origin

 operations/common-gpl3+/ripple.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/operations/common-gpl3+/ripple.c b/operations/common-gpl3+/ripple.c
index e1fe89f..8dbc6db 100644
--- a/operations/common-gpl3+/ripple.c
+++ b/operations/common-gpl3+/ripple.c
@@ -118,7 +118,7 @@ process (GeglOperation       *operation,
             gdouble lambda;
 
             gdouble angle_rad = o->angle / 180.0 * G_PI;
-            gdouble nx = x * cos (angle_rad) + y * sin (angle_rad);
+            gdouble nx = x * cos (angle_rad) - y * sin (angle_rad);
 
             switch (o->wave_type)
               {