Improved determine_object_boxes(). It will now avoid selecting object boxes

that redundant with detection templates already in a scanner object.

dlib/image_processing/scan_image_pyramid_tools.h

@@ -46,10 +46,19 @@ namespace dlib
 
         unsigned long max_area = 0;
 
-        // copy rects into sorted_rects and sort them in order of increasing area
+        // Copy rects into sorted_rects and sort them in order of increasing area.  But
+        // only include the rectangles that aren't already obtainable by the scanner.
         list_type sorted_rects;
         for (unsigned long i = 0; i < rects.size(); ++i)
         {
+            if (scanner.get_num_detection_templates() > 0)
+            {
+                rectangle temp = scanner.get_best_matching_rect(rects[i]);
+                const double match_score = (rects[i].intersect(temp).area())/(double)(rects[i] + temp).area();
+                // skip this rectangle if it's already matched well enough.
+                if (match_score > min_match_score)
+                    continue;
+            }
             max_area = std::max(rects[i].area(), max_area);
             sorted_rects.push_back(std::make_pair(rects[i].area(), rects[i]));
         }

dlib/image_processing/scan_image_pyramid_tools_abstract.h

@@ -26,11 +26,15 @@ namespace dlib
             - image_scanner_type == an implementation of the scan_image_pyramid
               object defined in dlib/image_processing/scan_image_pyramid_tools_abstract.h
         ensures
-            - returns a set of object boxes which, when used as detection
-              templates with the given scanner, can attain at least
-              min_match_score alignment with every element of rects.  Note that
-              the alignment between two rectangles A and B is defined as
+            - returns a set of object boxes which, when used as detection templates with
+              the given scanner, can attain at least min_match_score alignment with every
+              element of rects.  Note that the alignment between two rectangles A and B is
+              defined as:
                 (A.intersect(B).area())/(double)(A+B).area()
+            - Only elements of rects which are not already well matched by the scanner are
+              considered.  That is, if the scanner already has some detection templates in
+              it then the contents of rects will be checked against those detection
+              templates and elements with a match better than min_match_score are ignore.
     !*/
 
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