add angle bounding functions

src/UglyToad.PdfPig.DocumentLayoutAnalysis/Distances.cs

@@ -78,6 +78,28 @@
             return Math.Abs(point2.X - point1.X);
         }
 
+        /// <summary>
+        /// Bound angle so that -180 ≤ θ ≤ 180.
+        /// </summary>
+        /// <param name="angle">The angle to bound.</param>
+        public static double BoundAngle180(double angle)
+        {
+            angle = (angle + 180) % 360;
+            if (angle < 0) angle += 360;
+            return angle - 180;
+        }
+
+        /// <summary>
+        /// Bound angle so that 0 ≤ θ ≤ 360.
+        /// </summary>
+        /// <param name="angle">The angle to bound.</param>
+        public static double BoundAngle0to360(double angle)
+        {
+            angle %= 360;
+            if (angle < 0) angle += 360;
+            return angle;
+        }
+
         /// <summary>
         /// Get the minimum edit distance between two strings.
         /// </summary>