GlobalDescriptor (PyDescriptor / netvlad) (#1163)

* First commit for pydescriptor

* Fixed Python refactoring errors

* GUI: added PyDescriptor parameters

* reordered python3 includes

* updated rtabmap_netvlad.py test main

* fixed build from last merge

* integrated https://github.com/introlab/rtabmap/pull/1255

* rescaled dot product result

Closing https://github.com/introlab/rtabmap/issues/1105

corelib/src/python/PyDescriptor.h

@@ -0,0 +1,38 @@
+/**
+ * Python interface for python descriptors like:
+ *  - NetVLAD: https://github.com/uzh-rpg/netvlad_tf_open
+ */
+
+#ifndef PYDESCRIPTOR_H
+#define PYDESCRIPTOR_H
+
+#include <rtabmap/core/GlobalDescriptorExtractor.h>
+#include "rtabmap/core/PythonInterface.h"
+#include <Python.h>
+
+namespace rtabmap
+{
+
+class PyDescriptor : public GlobalDescriptorExtractor
+{
+public:
+  PyDescriptor(const ParametersMap & parameters = ParametersMap());
+  virtual ~PyDescriptor();
+
+  const std::string & path() const {return path_;}
+  float dim() const {return dim_;}
+
+  virtual void parseParameters(const ParametersMap & parameters);
+  virtual GlobalDescriptor extract(const SensorData & data) const;
+  virtual GlobalDescriptorExtractor::Type getType() const {return kPyDescriptor;}
+
+private:
+  PyObject * pModule_;
+  PyObject * pFunc_;
+  std::string path_;
+  int dim_;
+};
+
+}
+
+#endif