Example Detect Corners

From BoofCV

Corner features and other point features (e.g. Laplacian) are commonly used in SFM and 2D geometric applications. Perhaps the most well known corner feature is Shi-Tomasi (a.k.a. Good Features) and Harris corner features.

Example Code:

Concepts:

  • Image Features
  • SFM

Example Code

/**
 * Example showing how corner features can be detected. These features are not scale invariant, but are
 * fast to compute. In OpenCV Shi-Tomasi has the name of goodFeaturesToTrack and uses the unweighted variant.
 *
 * @author Peter Abeles
 */
public class ExampleCornerFeature {
	public static void main(String[] args) {
		ConfigGeneralDetector configNonMax = new ConfigGeneralDetector();
		// a large radius is used to exaggerate weighted/unweighted affects. Try 1 or 2 for a typical value
		configNonMax.radius = 10;
		configNonMax.threshold = 100;
		configNonMax.maxFeatures = 100;
		ConfigShiTomasi configCorner = new ConfigShiTomasi();
		configCorner.radius = configNonMax.radius; // in general you should use the same radius here
		configCorner.weighted = true;              // weighted corners will appear at the corners on a chessboard

		// set weighted to false and see what happens to the feature's locations. unweighted is much faster
		GeneralFeatureDetector<GrayU8,GrayS16> detector = FactoryDetectPoint.createShiTomasi(configNonMax,configCorner, GrayS16.class);
		ImageGradient<GrayU8, GrayS16> sobel = FactoryDerivative.sobel(GrayU8.class,GrayS16.class);

		BufferedImage image = UtilImageIO.loadImage(UtilIO.pathExample("calibration/mono/Sony_DSC-HX5V_Chess/frame05.jpg"));

		// Convert the image into a usable format and predeclare memory
		GrayU8 gray = ConvertBufferedImage.convertFrom(image,(GrayU8)null);
		GrayS16 derivX = new GrayS16(gray.width,gray.height);
		GrayS16 derivY = new GrayS16(gray.width,gray.height);

		// The first image derivatives are needed
		sobel.process(gray, derivX,derivY);

		// Compute the corners
		detector.process(gray,derivX,derivY,null,null,null);

		// Visualize the results
		QueueCorner corners = detector.getMaximums();
		Graphics2D g2 = image.createGraphics();
		for (int i = 0; i < corners.size; i++) {
			Point2D_I16 c = corners.get(i);
			VisualizeFeatures.drawPoint(g2,c.x,c.y,4,Color.RED,true);
		}

		ShowImages.showWindow(image,"Corners",true);
	}
}