Merge remote-tracking branch 'upstream/3.4' into merge-3.4

modules/features2d/CMakeLists.txt

@@ -1,2 +1,2 @@
 set(the_description "2D Features Framework")
-ocv_define_module(features2d opencv_imgproc OPTIONAL opencv_flann opencv_highgui WRAP java python)
+ocv_define_module(features2d opencv_imgproc OPTIONAL opencv_flann opencv_highgui WRAP java python js)

modules/features2d/include/opencv2/features2d.hpp

@@ -137,7 +137,11 @@ public:
 
 /** @brief Abstract base class for 2D image feature detectors and descriptor extractors
 */
+#ifdef __EMSCRIPTEN__
+class CV_EXPORTS_W Feature2D : public Algorithm
+#else
 class CV_EXPORTS_W Feature2D : public virtual Algorithm
+#endif
 {
 public:
     virtual ~Feature2D();

modules/features2d/src/matchers.cpp

@@ -40,7 +40,9 @@
 //M*/
 
 #include "precomp.hpp"
+#ifdef HAVE_OPENCV_FLANN
 #include "opencv2/flann/miniflann.hpp"
+#endif
 #include <limits>
 #include "opencl_kernels_features2d.hpp"