[gegl] contrast_curve: propagate BablSpace

[Øyvind "pippin" Kolås <ok src gnome org>]

commit 9afab8abe500d118dfbd4d7048f686f80a2808d8
Author: Øyvind Kolås <pippin gimp org>
Date:   Thu Jul 5 15:18:12 2018 +0200

    contrast_curve: propagate BablSpace

 operations/common/contrast-curve.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/operations/common/contrast-curve.c b/operations/common/contrast-curve.c
index 800e58953..d371eb06a 100644
--- a/operations/common/contrast-curve.c
+++ b/operations/common/contrast-curve.c
@@ -39,7 +39,8 @@ property_curve (curve, _("Curve"), NULL)
 
 static void prepare (GeglOperation *operation)
 {
-  const Babl *format = babl_format ("YA float");
+  const Babl *space = gegl_operation_get_source_space (operation, "input");
+  const Babl *format = babl_format_with_space ("YA float", space);
 
   gegl_operation_set_format (operation, "input", format);
   gegl_operation_set_format (operation, "output", format);