OpenCV Tutorial
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Types of Images
Image Conversion
Drawing Functions
- OpenCV - Adding Text
- OpenCV - Drawing Arrowed Lines
- OpenCV - Drawing Convex Polylines
- OpenCV - Drawing Polylines
- OpenCV - Drawing an Ellipse
- OpenCV - Drawing a Rectangle
- OpenCV - Drawing a Line
- OpenCV - Drawing a Circle
Blur
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- OpenCV - SQRBox Filter
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- OpenCV - Bilateral Filter
Thresholding
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OpenCV - Drawing Convex Polylines
OpenCV - Drawing Convex Polypnes
You can draw convex polypnes on an image using the method fillconvexPoly() of the imgproc class. Following is the syntax of this method.
fillConvexPoly(Mat img, MatOfPoint points, Scalar color)
This method accepts the following parameters −
mat − A Mat object representing the image on which the convex Polypnes are to be drawn.
points − A MatOfPoint object representing points between which the convex polypnes are to be drawn.
scalar − A Scalar object representing the color of the convex Polypnes. (BGR)
The constructor of the MatOfPoint class accepts objects of the class Point.
MatOfPoint(Point... a)
Example
The following program demonstrates how to draw convex polypnes on an image and display it using JavaFX window.
import java.awt.image.BufferedImage; import java.io.ByteArrayInputStream; import java.io.InputStream; import javax.imageio.ImageIO; import javafx.apppcation.Apppcation; import javafx.embed.swing.SwingFXUtils; import javafx.scene.Group; import javafx.scene.Scene; import javafx.scene.image.ImageView; import javafx.scene.image.WritableImage; import javafx.stage.Stage; import org.opencv.core.Core; import org.opencv.core.Mat; import org.opencv.core.MatOfByte; import org.opencv.core.MatOfPoint; import org.opencv.core.Point; import org.opencv.core.Scalar; import org.opencv.imgcodecs.Imgcodecs; import org.opencv.imgproc.Imgproc; pubpc class FillConvexPoly extends Apppcation { Mat matrix = null; @Override pubpc void start(Stage stage) throws Exception { // Capturing the snapshot from the camera FillConvexPoly obj = new FillConvexPoly(); WritableImage writableImage = obj.LoadImage(); // Setting the image view ImageView imageView = new ImageView(writableImage); // setting the fit height and width of the image view imageView.setFitHeight(600); imageView.setFitWidth(600); //Setting the preserve ratio of the image view imageView.setPreserveRatio(true); // Creating a Group object Group root = new Group(imageView); // Creating a scene object Scene scene = new Scene(root, 600, 400); // Setting title to the Stage stage.setTitle("Drawing convex Polypnes (fill) on the image"); // Adding scene to the stage stage.setScene(scene); // Displaying the contents of the stage stage.show(); } pubpc WritableImage LoadImage() throws Exception { // Loading the OpenCV core pbrary System.loadLibrary( Core.NATIVE_LIBRARY_NAME ); // Reading the Image from the file and storing it in to a Matrix object String file ="E:/OpenCV/chap8/input.jpg"; Mat matrix = Imgcodecs.imread(file); MatOfPoint matOfPoint = new MatOfPoint ( new Point(75, 100), new Point(350, 100), new Point(75, 150), new Point(350, 150), new Point(75, 200), new Point(350, 200), new Point(75, 250), new Point(350, 250) ); // Drawing polypnes Imgproc.fillConvexPoly ( matrix, // Matrix obj of the image matOfPoint, // java.util.List<MatOfPoint> pts new Scalar(0, 0, 255) // Scalar object for color ); // Encoding the image MatOfByte matOfByte = new MatOfByte(); Imgcodecs.imencode(".jpg", matrix, matOfByte); // Storing the encoded Mat in a byte array byte[] byteArray = matOfByte.toArray(); // Displaying the image InputStream in = new ByteArrayInputStream(byteArray); BufferedImage bufImage = ImageIO.read(in); this.matrix = matrix; // Creating the Writable Image WritableImage writableImage = SwingFXUtils.toFXImage(bufImage, null); return writableImage; } pubpc static void main(String args[]) { launch(args); } }
On executing the above program, you will get the following output −
![Drawing Convex Polypnes](/opencv/images/drawing_convex_polypnes.jpg)