Passing OpenCV contours from a JNI C++ function to Java in Android -

what best way pass opencv vector< std::vector<point > > contours jni c++ function java in android? current approach use arrays of doubles inefficient. there way use pointers maybe?

here's efficient way access contours wrapper javacpp presets opencv:

import org.bytedeco.javacpp.indexer.*; import static org.bytedeco.javacpp.opencv_core.*; import static org.bytedeco.javacpp.opencv_imgproc.*; import static org.bytedeco.javacpp.opencv_highgui.*;  public class contours {     public static void main(string[] args) {         mat grayscaleimage = imread("lena.png", cv_load_image_grayscale);         mat binarizedimage = new mat();         matvector contours = new matvector();         threshold(grayscaleimage, binarizedimage, 128, 255, thresh_binary);         findcontours(binarizedimage, contours, retr_list, chain_approx_none);         int contourssize = (int)contours.size();         system.out.println("size = " + contourssize);         (int contouridx = 0; contouridx < contourssize; contouridx++) {             // compute center             float x = 0, y = 0;             mat contour = contours.get(contouridx);             intindexer points = contour.createindexer(false);             int pointssize = contour.rows();             (int pointidx = 0; pointidx < pointssize; pointidx++) {                 x += points.get(pointidx, 0);                 y += points.get(pointidx, 1);             }             system.out.println("center = (" + x / pointssize + ", " + y / pointssize + ")");         }     } } 

for simplicity, i'm using java se, can same thing on android.