From 3265277468de1b140e656005fc0a9271d3e91329 Mon Sep 17 00:00:00 2001
From: Davis King <davis@dlib.net>
Date: Mon, 27 Feb 2012 20:04:57 -0500
Subject: [PATCH] Added dcenter(), point_transform_affine, and
 rotation_matrix()

---
 dlib/geometry/rectangle.h          | 12 ++++++++
 dlib/geometry/rectangle_abstract.h | 10 +++++++
 dlib/geometry/vector.h             | 39 ++++++++++++++++++++++++
 dlib/geometry/vector_abstract.h    | 48 ++++++++++++++++++++++++++++++
 4 files changed, 109 insertions(+)

diff --git a/dlib/geometry/rectangle.h b/dlib/geometry/rectangle.h
index 0b617a1a2..61f42dbe7 100644
--- a/dlib/geometry/rectangle.h
+++ b/dlib/geometry/rectangle.h
@@ -379,6 +379,18 @@ namespace dlib
         return temp/2;
     }
 
+// ----------------------------------------------------------------------------------------
+
+    inline dlib::vector<double,2> dcenter (
+        const dlib::rectangle& rect
+    )
+    {
+        dlib::vector<double,2> temp(rect.left() + rect.right(),
+                                    rect.top() + rect.bottom());
+
+        return temp/2.0;
+    }
+
 // ----------------------------------------------------------------------------------------
 
     inline long distance_to_rect_edge (
diff --git a/dlib/geometry/rectangle_abstract.h b/dlib/geometry/rectangle_abstract.h
index 14e185560..aab8a37ae 100644
--- a/dlib/geometry/rectangle_abstract.h
+++ b/dlib/geometry/rectangle_abstract.h
@@ -412,6 +412,16 @@ namespace dlib
             - returns the center of the given rectangle
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    dlib::vector<double,2> dcenter (
+        const dlib::rectangle& rect
+    );
+    /*!
+        ensures
+            - returns the center of the given rectangle using a real valued vector.  
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     inline const rectangle centered_rect (
diff --git a/dlib/geometry/vector.h b/dlib/geometry/vector.h
index 4133670b0..6ff4b7781 100644
--- a/dlib/geometry/vector.h
+++ b/dlib/geometry/vector.h
@@ -1319,6 +1319,30 @@ namespace dlib
         dlib::vector<double,2> translate;
     };
 
+// ----------------------------------------------------------------------------------------
+
+    class point_transform_affine
+    {
+    public:
+        point_transform_affine (
+            const matrix<double,2,2>& m_,
+            const dlib::vector<double,2>& b_
+        ) :m(m_), b(b_)
+        {
+        }
+
+        const dlib::vector<double,2> operator() (
+            const dlib::vector<double,2>& p
+        ) const
+        {
+            return m*p + b;
+        }
+
+    private:
+        matrix<double,2,2> m;
+        dlib::vector<double,2> b;
+    };
+
 // ----------------------------------------------------------------------------------------
 
     template <typename T>
@@ -1332,6 +1356,21 @@ namespace dlib
         return rot(p-center)+center;
     }
 
+// ----------------------------------------------------------------------------------------
+
+    inline matrix<double,2,2> rotation_matrix (
+         double angle
+    )
+    {
+        const double ca = cos(angle);
+        const double sa = sin(angle);
+
+        matrix<double,2,2> m;
+        m = ca, -sa,
+            sa, ca;
+        return m;
+    }
+
 // ----------------------------------------------------------------------------------------
 
 }
diff --git a/dlib/geometry/vector_abstract.h b/dlib/geometry/vector_abstract.h
index 482d66b8b..9cf98041b 100644
--- a/dlib/geometry/vector_abstract.h
+++ b/dlib/geometry/vector_abstract.h
@@ -431,6 +431,37 @@ namespace dlib
 
     typedef vector<long,2> point;
 
+// ----------------------------------------------------------------------------------------
+
+    class point_transform_affine
+    {
+        /*!
+            WHAT THIS OBJECT REPRESENTS
+                This is an object that takes 2D points or vectors and 
+                applies an affine transformation to them.
+        !*/
+    public:
+        point_transform_affine (
+            const matrix<double,2,2>& m,
+            const dlib::vector<double,2>& b
+        );
+        /*!
+            ensures
+                - When (*this)(p) is invoked it will return a point P such that:
+                    - P == m*p + b
+        !*/
+
+        const dlib::vector<double,2> operator() (
+            const dlib::vector<double,2>& p
+        ) const;
+        /*!
+            ensures
+                - applies the affine transformation defined by this object's constructor
+                  to p and returns the result.
+        !*/
+
+    };
+
 // ----------------------------------------------------------------------------------------
 
     class point_transform
@@ -517,6 +548,23 @@ namespace dlib
                   to the right)
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    matrix<double,2,2> rotation_matrix (
+         double angle
+    );
+    /*!
+        ensures
+            - returns a rotation matrix which rotates points around the origin in a
+              counter-clockwise direction by angle radians.
+              (Note that this is counter clockwise with respect to the normal
+              coordinate system with positive y going up and positive x going
+              to the right)
+              Or in other words, this function returns a matrix M such that, given a
+              point P, M*P gives a point which is P rotated by angle radians around
+              the origin in a counter-clockwise direction.
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
 }