OpenCV - 绘制凸多边形

您可以使用 imgproc 类中的 fillconvexPoly() 方法在图像上绘制凸多边形。以下是此方法的语法。

fillConvexPoly(Mat img, MatOfPoint points, Scalar color)

此方法接受以下参数：

• mat − 一个 Mat 对象，表示要绘制凸多边形的图像。

• points − 一个 MatOfPoint 对象，表示要绘制凸多边形之间的点。

• scalar − 一个 Scalar 对象，表示凸多边形的颜色。（BGR）

MatOfPoint 类的构造函数接受 Point 类对象。

MatOfPoint(Point... a)

示例

以下程序演示了如何在图像上绘制凸多边形并在 JavaFX 窗口中显示它。

import java.awt.image.BufferedImage;

import java.io.ByteArrayInputStream;
import java.io.InputStream;
import javax.imageio.ImageIO;

import javafx.application.Application;
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;

public class FillConvexPoly extends Application {
   Mat matrix = null;

   @Override
   public 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 Polylines (fill) on the image");

      // Adding scene to the stage
      stage.setScene(scene);

      // Displaying the contents of the stage
      stage.show();
   }
   public WritableImage LoadImage() throws Exception {
      // Loading the OpenCV core library
      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 polylines
      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;
   } 
   public static void main(String args[]) {
      launch(args);
   }
}

执行上述程序后，您将获得以下输出：