Added an unload() to the hog_image.

dlib/image_keypoint/hashed_feature_image.h

@@ -245,18 +245,17 @@ namespace dlib
         const image_type& img
     )
     {
-        feature_extractor fe_temp;
-        fe_temp.copy_configuration(fe);
-        fe_temp.load(img);
+        fe.load(img);
 
-        feats.set_size(fe_temp.nr(), fe_temp.nc());
+        feats.set_size(fe.nr(), fe.nc());
         for (long r = 0; r < feats.nr(); ++r)
         {
             for (long c = 0; c < feats.nc(); ++c)
             {
-                feats[r][c] = phash(fe_temp(r,c));
+                feats[r][c] = phash(fe(r,c));
             }
         }
+        fe.unload();
     }
 
 // ----------------------------------------------------------------------------------------

dlib/image_keypoint/hog.h

@@ -86,6 +86,9 @@ namespace dlib
             load_impl(array_to_matrix(img));
         }
 
+        inline void unload(
+        ) { clear(); }
+
         inline unsigned long size (
         ) const { return static_cast<unsigned long>(nr()*nc()); }
 

dlib/image_keypoint/hog_abstract.h

@@ -169,6 +169,25 @@ namespace dlib
                     - #size() > 0
         !*/
 
+        inline void unload (
+        );
+        /*!
+            ensures
+                - #nr() == 0
+                - #nc() == 0
+                - clears only the state information which is populated by load().  For 
+                  example, let H be a hog_image object.  Then consider the two sequences 
+                  of instructions:
+                    Sequence 1:
+                        H.load(img);      
+                        H.unload();
+                        H.load(img);
+
+                    Sequence 2:
+                        H.load(img);
+                  Both sequence 1 and sequence 2 should have the same effect on H.  
+        !*/
+
         inline unsigned long size (
         ) const;
         /*!