title: Keypoint detection and matching for large images in opencv
body: <p>I am doing keypoint detection and matching in opencv to stitch two images.</p>
  
  <p>When the images are small, it works well. But when dealing with larger images, the number of keypoints detected is increased, and therefore it cost a lot of time to match them. But in order to stitch the images, it seems that we don't need so many keypoints. In order to increase efficiency, is there any way to only detect a limited number of keypoints? </p>
  
  <p>In the code, I use SiftFeatureDetector and SiftDiscriptorExtractor to detect keypoints and extract descriptors.</p>
  
  <p>Regards.</p>