Added the ability to threshold out length's outside a certain range into

the squared_euclidean_distance object.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403656

dlib/manifold_regularization/function_objects.h

@@ -6,6 +6,7 @@
 #include "function_objects_abstract.h"
 #include "../matrix.h"
 #include <cmath>
+#include <limits>
 
 namespace dlib
 {
@@ -14,13 +15,34 @@ namespace dlib
 
     struct squared_euclidean_distance
     {
+        squared_euclidean_distance (
+        ) : 
+            lower(0),
+            upper(std::numeric_limits<double>::infinity())
+        {}
+
+        squared_euclidean_distance (
+            const double l,
+            const double u
+        ) :
+            lower(l),
+            upper(u)
+        {}
+
+        const double lower;
+        const double upper;
+
         template <typename sample_type>
         double operator() (
             const sample_type& a,
             const sample_type& b
         ) const
         { 
-            return length_squared(a-b);
+            const double len = length_squared(a-b);
+            if (lower <= len && len <= upper)
+                return len;
+            else
+                return std::numeric_limits<double>::infinity();
         }
     };
 

dlib/manifold_regularization/function_objects_abstract.h

@@ -16,9 +16,30 @@ namespace dlib
         /*!
             WHAT THIS OBJECT REPRESENTS
                 This is a simple function object that computes squared euclidean distance
-                between two dlib::matrix objects.
+                between two dlib::matrix objects. 
         !*/
 
+        squared_euclidean_distance (
+        );
+        /*!
+            ensures
+                - #lower == 0
+                - #upper == std::numeric_limits<double>::infinity()
+        !*/
+
+        squared_euclidean_distance (
+            const double l,
+            const double u
+        );
+        /*!
+            ensures
+                - #lower == l
+                - #upper == u  
+        !*/
+
+        const double lower;
+        const double upper;
+
         template <typename sample_type>
         double operator() (
             const sample_type& a,
@@ -28,7 +49,11 @@ namespace dlib
             requires
                 - sample_type should be a kind of dlib::matrix 
             ensures
-                - returns length_squared(a-b);
+                - let LEN = length_squared(a-b)
+                - if (lower <= LEN <= upper) then
+                    - returns LEN
+                - else
+                    - returns std::numeric_limits<double>::infinity()
         !*/
     };