opencv/samples/android/tutorial-4-mixed/jni/jni_part.cpp

#include <jni.h>
#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/features2d/features2d.hpp>
#include <vector>

using namespace std;
using namespace cv;

extern "C" {
JNIEXPORT void JNICALL Java_org_opencv_samples_tutorial4_Sample4Mixed_FindFeatures(JNIEnv*, jobject, jlong addrGray, jlong addrRgba)
{
    Mat* pMatGr=(Mat*)addrGray;
    Mat* pMatRgb=(Mat*)addrRgba;
    vector<KeyPoint> v;

    FastFeatureDetector detector(50);
    detector.detect(*pMatGr, v);
    for( size_t i = 0; i < v.size(); i++ )
        circle(*pMatRgb, Point(v[i].pt.x, v[i].pt.y), 10, Scalar(255,0,0,255));
}

}