Building opencv Rect wrapper C++ Java (swig)

Question

Hi I've been dealing with this for some time now. I would like to make a wrapper for the cv::Rect object in C++ and the org.opencv.core.Rect in Java.

I'm returning a std::vector in c++ and I would like to get a template build with swig called RectangleVector (%template(RectangleVector) std::vector).

For now I have the following code:

%typemap(jstype) cv::Rect "org.opencv.core.Rect" 
%typemap(jtype) cv::Rect "org.opencv.core.Rect" 
%typemap(jni) cv::Rect "jobject" 
%typemap(javaout) cv::Rect {
    return $jnicall;
}
%typemap(out) cv::Rect{ 
jclass jRectClass = jenv->FindClass("org/opencv/core/Rect");
jmethodID jRectConstructor = jenv->GetMethodID(jRectClass, "<init>", "(IIII)V");
jobject jRect = jenv->NewObject(jRectClass, jRectConstructor, $1.x, $1.y, $1.width, $1.height);
    $result = jRect;
}
%typemap(javaimports) FaceDetector "import org.opencv.core.Mat;import org.opencv.core.Rect;"

To deal with the std::vector I followed this link [SWIG (v1.3.29) generated C++ to Java Vector class not acting properly. Replacing the Double by the cv::Rect:

%{
#include <vector>
#include <stdexcept>
#include <opencv2/opencv.hpp>
%}

%include <stdint.i>
%include <std_except.i>

namespace std {

template<class T> class vector {
  public:
    typedef size_t size_type;
    typedef T value_type;
    typedef const value_type& const_reference;
    %rename(size_impl) size;
    vector();
    vector(size_type n);
    size_type size() const;
    size_type capacity() const;
    void reserve(size_type n);
    %rename(isEmpty) empty;
    bool empty() const;
    void clear();
    void push_back(const value_type& x);
    %extend {
        const_reference get_impl(int i) throw (std::out_of_range) {
            // at will throw if needed, swig will handle
            return self->at(i);
        }
        void set_impl(int i, const value_type& val) throw (std::out_of_range) {
            // at can throw
            self->at(i) = val;
        }
    }
};
}

%typemap(javabase) std::vector<cv::Rect> "java.util.AbstractList<org.opencv.core.Rect>"
%typemap(javainterface) std::vector<cv::Rect> "java.util.RandomAccess"
%typemap(javacode) std::vector<cv::Rect> %{
    public org.opencv.core.Rect get(int idx) {
        return get_impl(idx);
    }
    public int size() {
        return (int)size_impl();
    }
    public org.opencv.core.Rect set(int idx, org.opencv.core.Rect r) {
        org.opencv.core.Rect old = get_impl(idx);
        set_impl(idx, r);
        return old;
    }
%}
%template(RectangleVector) std::vector<cv::Rect>;

When i'm compiling the Java files I get the following error:

RectangleVector.java:39: error: incompatible types: SWIGTYPE_p_cv__Rect cannot be converted to Rect
    return get_impl(idx);
                   ^

RectangleVector.java:45: error: incompatible types: SWIGTYPE_p_cv__Rect cannot be converted to Rect
    org.opencv.core.Rect old = get_impl(idx);
                                       ^

RectangleVector.java:46: error: incompatible types: Rect cannot be converted to SWIGTYPE_p_cv__Rect
    set_impl(idx, r);

I think I should implement the %typemap(javain) and %typemap(in) typesmaps for cv::Rect but I'm not certain how to do it.

I based myself on the following links (since i'm using dlib, cmake and swig too):

https://www.anyline.io/blog/2016/02/25/how-to-glue-java-and-c-together-using-swig-and-type-maps-part-i/ https://github.com/mit-nlp/MITIE/tree/master/mitielib/java