[gegl] spiral: invert "balance" direction

[N/A <ell src gnome org>]

commit a5d4cd264a55756aa2b0a52059c051de7c5e1556
Author: Ell <ell_se yahoo com>
Date:   Mon May 15 11:39:07 2017 -0400

    spiral: invert "balance" direction
    
    ... so that positive values increase the relative area of color1,
    and negative values increase the relative area of color2.  Feels
    more natural.

 operations/workshop/spiral.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/operations/workshop/spiral.c b/operations/workshop/spiral.c
index b031220..7e26a64 100644
--- a/operations/workshop/spiral.c
+++ b/operations/workshop/spiral.c
@@ -382,7 +382,7 @@ process (GeglOperation       *operation,
   gfloat          x0;
   gfloat          y0;
   gfloat          radius    = scale * o->radius;
-  gfloat          thickness = (1.0 - o->balance) / 2.0;
+  gfloat          thickness = (1.0 + o->balance) / 2.0;
   gfloat          angle     = o->rotation / 360.0;
   gboolean        clockwise = o->direction == GEGL_SPIRAL_DIRECTION_CLOCKWISE;
   gfloat          color1[4];