modules/png/graphics/ellipse (draw!): Bugfix

* modules/png/graphics/ellipse.scm (draw!): Bugfix: Convert rational numbers
  to exact values in ellipse center calculations.
* NEWS: Update.

NEWS

@@ -7,6 +7,11 @@ Copyright (C) Artyom V. Poptsov <[email protected]>
   are permitted in any medium without royalty provided the copyright
   notice and this notice are preserved.
 
+* Unreleased
+** Fix ellipse drawing                                               :BUGFIX:
+Guile-PNG would fail to draw an ellipse at the specified position due to
+rational number calculation errors.  Now it is fixed.
+
 * Changes in version 0.7.1 (2023-08-20)
 ** Fix Bresenham's Line generation algorithm                         :BUGFIX:
 Bresenham's Line generation algorithm would fail to draw properly some types

modules/png/graphics/ellipse.scm

@@ -51,8 +51,8 @@
   (let* ((center (ellipse-center ellipse))
          (width  (ellipse-width ellipse))
          (height (ellipse-height ellipse))
-         (rx     (/ width 2))
-         (ry     (/ height 2))
+         (rx     (inexact->exact (floor (/ width 2.0))))
+         (ry     (inexact->exact (floor (/ height 2.0))))
          (color  (graphic-color ellipse)))
 
     (define* (draw-region-2 #:key x y d2 dx dy)