Added another constructor to object_detector that makes it easy to combine

multiple detectors together.

dlib/image_processing/object_detector.h

@@ -73,6 +73,10 @@ namespace dlib
             const std::vector<feature_vector_type>& w_ 
         );
 
+        explicit object_detector (
+            const std::vector<object_detector>& detectors
+        );
+
         unsigned long num_detectors (
         ) const { return w.size(); }
 
@@ -356,6 +360,32 @@ namespace dlib
         }
     }
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename image_scanner_type
+        >
+    object_detector<image_scanner_type>::
+    object_detector (
+        const std::vector<object_detector>& detectors
+    )
+    {
+        DLIB_ASSERT(detectors.size() != 0,
+                "\t object_detector::object_detector(detectors)"
+                << "\n\t Invalid inputs were given to this function "
+                << "\n\t this: " << this
+        );
+        std::vector<feature_vector_type> weights;
+        weights.reserve(detectors.size());
+        for (unsigned long i = 0; i < detectors.size(); ++i)
+        {
+            for (unsigned long j = 0; j < detectors[i].num_detectors(); ++j)
+                weights.push_back(detectors[i].get_w(j));
+        }
+
+        *this = object_detector(detectors[0].get_scanner(), detectors[0].get_overlap_tester(), weights);
+    }
+
 // ----------------------------------------------------------------------------------------
 
     template <

dlib/image_processing/object_detector_abstract.h

@@ -110,7 +110,7 @@ namespace dlib
                 - w.size() > 0
             ensures
                 - When the operator() member function is called it will invoke
-                  scanner.detect(w[i],dets,w[i](w[i].size()-1)) for all valid i.  Then it
+                  get_scanner().detect(w[i],dets,w[i](w[i].size()-1)) for all valid i.  Then it
                   will take all the detections output by the calls to detect() and suppress
                   overlapping detections, and finally report the results.
                 - when #*this is used to detect objects, the set of output detections will
@@ -126,6 +126,34 @@ namespace dlib
                   I.e. the copy is done using copy_configuration())
         !*/
 
+        explicit object_detector (
+            const std::vector<object_detector>& detectors
+        );
+        /*!
+            requires
+                - detectors.size() != 0
+                - All the detectors must use compatibly configured scanners.  That is, it
+                  must make sense for the weight vector from one detector to be used with
+                  the scanner from any other.
+                - for all valid i:
+                    - detectors[i].get_scanner().get_num_dimensions() == detectors[0].get_scanner().get_num_dimensions()
+                      (i.e. all the detectors use scanners that use the same kind of feature vectors.)
+            ensures
+                - Very much like the above constructor, this constructor takes all the
+                  given detectors and packs them into #*this.  That is, invoking operator()
+                  on #*this will run all the detectors, perform non-max suppression, and
+                  then report the results.
+                - When #*this is used to detect objects, the set of output detections will
+                  never contain any overlaps with respect to overlap_tester.  That is, for
+                  all pairs of returned detections A and B, we will always have:
+                    overlap_tester(A,B) == false
+                - #num_detectors() == The sum of detectors[i].num_detectors() for all valid i. 
+                - #get_overlap_tester() == detectors[0].get_overlap_tester()
+                - #get_scanner() == detectors[0].get_scanner()
+                  (note that only the "configuration" of scanner is copied.  I.e. the copy
+                  is done using copy_configuration())
+        !*/
+
         unsigned long num_detectors (
         ) const; 
         /*!