[gegl] png-save: Use gamma corrected also in non-alpha case

[Jon Nordby <jonnor src gnome org>]

commit 56288e5df7b79b81376ff6f0e4cc97c59563dea2
Author: Jon Nordby <jononor gmail com>
Date:   Sun Oct 2 19:59:17 2011 +0200

    png-save: Use gamma corrected also in non-alpha case

 operations/external/png-save.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/operations/external/png-save.c b/operations/external/png-save.c
index c1f02ac..7417bc0 100644
--- a/operations/external/png-save.c
+++ b/operations/external/png-save.c
@@ -114,12 +114,12 @@ gegl_buffer_export_png (GeglBuffer  *gegl_buffer,
       if (babl_format_get_n_components (babl) != 1)
         {
           png_color_type = PNG_COLOR_TYPE_RGB;
-          strcpy (format_string, "RGB ");
+          strcpy (format_string, "R'G'B' ");
         }
       else
         {
           png_color_type = PNG_COLOR_TYPE_GRAY;
-          strcpy (format_string, "Y ");
+          strcpy (format_string, "Y' ");
         }
   }