/**
  * Detects keypoints in an image (first variant) or image set (second variant).
  *
  * @param images Image set.
  * @param keypoints The detected keypoints. In the second variant of the method <code>keypoints[i]
  *     </code> is a set of keypoints detected in <code>images[i]</code>.
  * @see <a
  *     href="http://docs.opencv.org/modules/features2d/doc/common_interfaces_of_feature_detectors.html#featuredetector-detect">org.opencv.features2d.FeatureDetector.detect</a>
  */
 public void detect(List<Mat> images, List<MatOfKeyPoint> keypoints) {
   Mat images_mat = Converters.vector_Mat_to_Mat(images);
   Mat keypoints_mat = new Mat();
   detect_3(nativeObj, images_mat.nativeObj, keypoints_mat.nativeObj);
   Converters.Mat_to_vector_vector_KeyPoint(keypoints_mat, keypoints);
   return;
 }