Added sum_filter_assign().

dlib/image_transforms/spatial_filtering.h

@@ -621,7 +621,10 @@ namespace dlib
 
 // ----------------------------------------------------------------------------------------
 
+    namespace impl
+    {
     template <
+        bool add_to,
         typename image_type1, 
         typename image_type2
         >
@@ -710,10 +713,40 @@ namespace dlib
                 // add in the new right side of the rect and subtract the old right side.
                 cur_sum = cur_sum + column_sum[c+width] - column_sum[c];
 
-                out[r][c] += static_cast<typename image_type2::type>(cur_sum);
+                if (add_to)
+                    out[r][c] += static_cast<typename image_type2::type>(cur_sum);
+                else
+                    out[r][c] = static_cast<typename image_type2::type>(cur_sum);
             }
         }
     }
+    }
+
+    template <
+        typename image_type1, 
+        typename image_type2
+        >
+    void sum_filter (
+        const image_type1& img,
+        image_type2& out,
+        const rectangle& rect
+    )
+    {
+        impl::sum_filter<true>(img,out,rect);
+    }
+
+    template <
+        typename image_type1, 
+        typename image_type2
+        >
+    void sum_filter_assign (
+        const image_type1& img,
+        image_type2& out,
+        const rectangle& rect
+    )
+    {
+        impl::sum_filter<false>(img,out,rect);
+    }
 
 // ----------------------------------------------------------------------------------------
 

dlib/image_transforms/spatial_filtering_abstract.h

@@ -338,6 +338,33 @@ namespace dlib
                 - #out[r][c] == out[r][c] + SUM(r,c)
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename image_type1, 
+        typename image_type2
+        >
+    void sum_filter_assign (
+        const image_type1& img,
+        image_type2& out,
+        const rectangle& rect
+    );
+    /*!
+        requires
+            - out.nr() == img.nr() 
+            - out.nc() == img.nc()
+            - image_type1 == an implementation of array2d/array2d_kernel_abstract.h
+              and it must contain a scalar type
+            - image_type2 == an implementation of array2d/array2d_kernel_abstract.h
+              and it must contain a scalar type
+            - is_same_object(img,out) == false
+        ensures
+            - for all valid r and c:
+                - let SUM(r,c) == sum of pixels from img which are inside the rectangle 
+                  translate_rect(rect, point(c,r)).
+                - #out[r][c] == SUM(r,c)
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     template <