Added add_image_left_right_flips()

dlib/image_transforms/interpolation.h

@@ -578,6 +578,60 @@ namespace dlib
         assign_image(out_img, flipud(mat(in_img)));
     }
 
+// ----------------------------------------------------------------------------------------
+
+    namespace impl
+    {
+        inline rectangle flip_rect_left_right (
+            const rectangle& rect,
+            const rectangle& window 
+        )
+        {
+            rectangle temp;
+            temp.top() = rect.top();
+            temp.bottom() = rect.bottom();
+
+            const long left_dist = rect.left()-window.left();
+
+            temp.right() = window.right()-left_dist; 
+            temp.left()  = temp.right()-rect.width()+1; 
+            return temp;
+        }
+    }
+
+    template <
+        typename image_type
+        >
+    void add_image_left_right_flips (
+        dlib::array<image_type>& images,
+        std::vector<std::vector<rectangle> >& objects
+    )
+    {
+        // make sure requires clause is not broken
+        DLIB_ASSERT( images.size() == objects.size(),
+            "\t void add_image_left_right_flips()"
+            << "\n\t Invalid inputs were given to this function."
+            << "\n\t images.size():  " << images.size() 
+            << "\n\t objects.size(): " << objects.size() 
+            );
+
+        image_type temp;
+        std::vector<rectangle> rects;
+
+        const unsigned long num = images.size();
+        for (unsigned long j = 0; j < num; ++j)
+        {
+            flip_image_left_right(images[j], temp);
+
+            rects.clear();
+            for (unsigned long i = 0; i < objects[j].size(); ++i)
+                rects.push_back(impl::flip_rect_left_right(objects[j][i], get_rect(images[j])));
+
+            images.push_back(temp);
+            objects.push_back(rects);
+        }
+    }
+
 // ----------------------------------------------------------------------------------------
 
     namespace impl

dlib/image_transforms/interpolation_abstract.h

@@ -421,6 +421,31 @@ namespace dlib
               (i.e. it is flipped as if viewed though a mirror)
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename image_type
+        >
+    void add_image_left_right_flips (
+        dlib::array<image_type>& images,
+        std::vector<std::vector<rectangle> >& objects
+    );
+    /*!
+        requires
+            - image_type == is an implementation of array2d/array2d_kernel_abstract.h
+            - pixel_traits<typename image_type::type> is defined
+            - images.size() == objects.size()
+        ensures
+            - This function computes all the left/right flips of the contents of images and
+              then appends them onto the end of the images array.  It also finds the
+              left/right flips of the rectangles in objects and similarly appends them into
+              objects.  That is, we assume objects[i] is the set of bounding boxes in
+              images[i] and we flip the bounding boxes so that they still bound the same
+              objects in the new flipped images.
+            - #images.size() == images.size()*2
+            - #objects.size() == objects.size()*2
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     template <