[gegl] gegl:dither improve ui defaults

[Øyvind Kolås <ok src gnome org>]

commit 1b1dbdbb54e258d3ed268c022aaa142bc235b1e1
Author: Øyvind Kolås <pippin gimp org>
Date:   Sat Dec 24 20:18:15 2016 +0100

    gegl:dither improve ui defaults
    
    Add a nonlinearity to ui gamma of each R, G, B, A, change default dithering
    method to floyd-steinberg, and change default levels to red 6, green 7, blue 6
    which is an RGB cube fitting in 252 slots, suitable for indexed conversion.

 operations/common/dither.c |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)
---
diff --git a/operations/common/dither.c b/operations/common/dither.c
index 945eb18..65e20f3 100644
--- a/operations/common/dither.c
+++ b/operations/common/dither.c
@@ -24,24 +24,28 @@
 
 #ifdef GEGL_PROPERTIES
 
-property_int  (red_levels, _("Red levels"), 256)
+property_int  (red_levels, _("Red levels"), 6)
     description(_("Number of levels for red channel"))
     value_range (2, 65536)
+    ui_gamma (4.0)
 
-property_int  (green_levels, _("Green levels"), 256)
+property_int  (green_levels, _("Green levels"), 7)
     description(_("Number of levels for green channel"))
     value_range (2, 65536)
+    ui_gamma (4.0)
 
-property_int  (blue_levels, _("Blue levels"), 256)
+property_int  (blue_levels, _("Blue levels"), 6)
     description(_("Number of levels for blue channel"))
     value_range (2, 65536)
+    ui_gamma (4.0)
 
 property_int  (alpha_levels, _("Alpha levels"), 256)
     description(_("Number of levels for alpha channel"))
     value_range (2, 65536)
+    ui_gamma (5.0)
 
 property_enum (dither_method, _("Dithering method"),
-               GeglDitherMethod, gegl_dither_method, GEGL_DITHER_RESILIENT)
+               GeglDitherMethod, gegl_dither_method, GEGL_DITHER_FLOYD_STEINBERG)
     description (_("The dithering method to use"))
 
 property_seed (seed, _("Random seed"), rand)