Added a global operator+ for rectangle+point to make this kind of operation

compile in more contexts.

dlib/geometry/rectangle.h

@@ -541,6 +541,26 @@ namespace dlib
         return rectangle(0, 0, m.nc()-1, m.nr()-1);
     }
 
+// ----------------------------------------------------------------------------------------
+
+    inline rectangle operator+ (
+        const rectangle& r,
+        const point& p
+    )
+    {
+        return r + rectangle(p);
+    }
+
+// ----------------------------------------------------------------------------------------
+
+    inline rectangle operator+ (
+        const point& p,
+        const rectangle& r
+    )
+    {
+        return r + rectangle(p);
+    }
+
 // ----------------------------------------------------------------------------------------
 
 }

dlib/geometry/rectangle_abstract.h

@@ -636,6 +636,30 @@ namespace dlib
               bounding rectangle for that gridded object.)
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    inline rectangle operator+ (
+        const rectangle& r,
+        const point& p
+    );
+    /*!
+        ensures
+            - returns r + rectangle(p)
+              (i.e. returns the rectangle that contains both r and p)
+    !*/
+
+// ----------------------------------------------------------------------------------------
+
+    inline rectangle operator+ (
+        const point& p,
+        const rectangle& r
+    );
+    /*!
+        ensures
+            - returns r + rectangle(p)
+              (i.e. returns the rectangle that contains both r and p)
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
 }

dlib/test/geometry.cpp

@@ -346,6 +346,9 @@ namespace
 
         }
 
+
+        DLIB_TEST(rectangle() + point(5,4) + point(10,10) == rectangle(5,4,10,10));
+
     }