private void btnSurf_Click(object sender, EventArgs e)
{
// Step 1: Detect feature points using Surf Corners Detector
SpeededUpRobustFeaturesDetector surf = new SpeededUpRobustFeaturesDetector();
surfPoints1 = surf.ProcessImage(img1).ToArray();
surfPoints2 = surf.ProcessImage(img2).ToArray();
// Show the marked points in the original images
Bitmap img1mark = new FeaturesMarker(surfPoints1).Apply(img1);
Bitmap img2mark = new FeaturesMarker(surfPoints2).Apply(img2);
// Concatenate the two images together in a single image (just to show on screen)
Concatenate concatenate = new Concatenate(img1mark);
pictureBox.Image = concatenate.Apply(img2mark);
}