How to return Opencv Mat object from native c++ to java ?

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C++

Java

JNI

OpenCV

I want to access c++ code from java program. For that I used concept of JNI.
I declare one native method in java, whose return type is Mat class of opencv, as follows :

public native Mat getFrames();

Then using javah utility, I created c implementation(Header File) of my java class JNITest.h using command : javah -jni java_class_name. This header file is as follows :

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class JNITest */

#ifndef _Included_JNITest
#define _Included_JNITest
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     JNITest
 * Method:    getFrames
 * Signature: ()Lorg/opencv/core/Mat;
 */
JNIEXPORT jobject JNICALL Java_JNITest_getFrames(JNIEnv *, jobject);

#ifdef __cplusplus
}
#endif
#endif

I implement this Java_JNITest_getFrames method in cpp file as follows:

JNIEXPORT jobject JNICALL Java_JNITest_getFrames(JNIEnv *en, jobject)
{
    Mat frame;
    VideoCapture cap("D:\\ImageProcessing\\1.jpg");
    cap>>frame;
    jobject jb ;
    Mat * ptrImg = &frame;
    jb=(jobject)ptrImg;
    return jb;
}

But, this above code is not working.
So, how to convert opencv Mat class object to this jobject ?
And how do I return that object ?