[gimp] Issue #2405 - Rotation center shifts by half a pixel ...

[Ell <ell src gnome org>]

commit c271992aa01dc8d565524ade8f511f4932c307fd
Author: Ell <ell_se yahoo com>
Date:   Sat Oct 27 00:07:22 2018 -0400

    Issue #2405 - Rotation center shifts by half a pixel ...
    
    ... the second time you do a 180 degrees rotation
    
    In gimp_transform_resize_adjust(), nudge the transformed layer
    boundary by EPSILON toward the center, to avoid enlarging the layer
    unnecessarily, as a result of numeric error amplified by rounding,
    when the tranformed boundary should land on integer coordinates.
    In particular, this avoids enlarging the layer when rotating by 180
    degrees.

 app/core/gimp-transform-resize.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/app/core/gimp-transform-resize.c b/app/core/gimp-transform-resize.c
index 059a3413e1..50e44d6f4a 100644
--- a/app/core/gimp-transform-resize.c
+++ b/app/core/gimp-transform-resize.c
@@ -233,11 +233,11 @@ gimp_transform_resize_adjust (const GimpVector2 *points,
       bottom_right.y = MAX (bottom_right.y, points[i].y);
     }
 
-  *x1 = (gint) floor (top_left.x);
-  *y1 = (gint) floor (top_left.y);
+  *x1 = (gint) floor (top_left.x + EPSILON);
+  *y1 = (gint) floor (top_left.y + EPSILON);
 
-  *x2 = (gint) ceil (bottom_right.x);
-  *y2 = (gint) ceil (bottom_right.y);
+  *x2 = (gint) ceil (bottom_right.x - EPSILON);
+  *y2 = (gint) ceil (bottom_right.y - EPSILON);
 }
 
 static void