[gegl] operations: fix an iterator access flag in image-compare

[Téo Mazars <teom src gnome org>]

commit b4b2374c62da350db1487f852d19a7a5208d2d70
Author: Téo Mazars <teo mazars ensimag fr>
Date:   Wed Oct 16 17:02:13 2013 +0200

    operations: fix an iterator access flag in image-compare

 operations/common/image-compare.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/operations/common/image-compare.c b/operations/common/image-compare.c
index 93b2a6c..eb41297 100644
--- a/operations/common/image-compare.c
+++ b/operations/common/image-compare.c
@@ -97,7 +97,7 @@ process (GeglOperation       *operation,
   diff_buffer = gegl_buffer_new (result, yadbl);
 
   iter = gegl_buffer_iterator_new (diff_buffer, result, 0, yadbl,
-                                   GEGL_BUFFER_READ, GEGL_ABYSS_NONE);
+                                   GEGL_BUFFER_WRITE, GEGL_ABYSS_NONE);
 
   gegl_buffer_iterator_add (iter, input, result, 0, cielab,
                             GEGL_BUFFER_READ, GEGL_ABYSS_NONE);