Merge pull request #641 from alessiodore:kcfFix

* Fix kcfTracker when called from Python bindings. The variable boundingBox in updateImpl when called from Python is initialized with 0s and it needs to be updated with the tracker state.

* Fix to return the bbox correctly in the first frame in Python

modules/tracking/src/trackerKCF.cpp

@@ -336,12 +336,14 @@ namespace cv{
       minMaxLoc( response, &minVal, &maxVal, &minLoc, &maxLoc );
       roi.x+=(maxLoc.x-roi.width/2+1);
       roi.y+=(maxLoc.y-roi.height/2+1);
-
-      // update the bounding box
-      boundingBox.x=(resizeImage?roi.x*2:roi.x)+boundingBox.width/2;
-      boundingBox.y=(resizeImage?roi.y*2:roi.y)+boundingBox.height/2;
     }
 
+    // update the bounding box
+    boundingBox.x=(resizeImage?roi.x*2:roi.x)+(resizeImage?roi.width*2:roi.width)/4;
+    boundingBox.y=(resizeImage?roi.y*2:roi.y)+(resizeImage?roi.height*2:roi.height)/4;
+    boundingBox.width = (resizeImage?roi.width*2:roi.width)/2;
+    boundingBox.height = (resizeImage?roi.height*2:roi.height)/2;
+
     // extract the patch for learning purpose
     // get non compressed descriptors
     for(unsigned i=0;i<descriptors_npca.size()-extractor_npca.size();i++){