[SL.Core] add center property to rectangle

src/SixLabors.Core/Primitives/Rectangle.cs

@@ -110,6 +110,16 @@ namespace SixLabors.Primitives
             }
         }
 
+        /// <summary>
+        /// Gets the coordinates of the center of the rectangular region represented by this <see cref="RectangleF"/>.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public Point Center
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => new Point(this.X + (this.Width / 2), this.Y + (this.Height / 2));
+        }
+
         /// <summary>
         /// Gets a value indicating whether this <see cref="Rectangle"/> is empty.
         /// </summary>

src/SixLabors.Core/Primitives/RectangleF.cs

@@ -110,6 +110,16 @@ namespace SixLabors.Primitives
             }
         }
 
+        /// <summary>
+        /// Gets the coordinates of the center of the rectangular region represented by this <see cref="RectangleF"/>.
+        /// </summary>
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public PointF Center
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => new PointF(this.X + (this.Width / 2), this.Y + (this.Height / 2));
+        }
+
         /// <summary>
         /// Gets a value indicating whether this <see cref="RectangleF"/> is empty.
         /// </summary>