在本章中，我們將學習如何使用OpenCV使用系統攝像機捕捉幀。org.opencv.videoio包的video capture類包含使用相機捕獲視頻的類和方法。讓我們一步一步地學習如何捕捉幀−

Step 1: Load the OpenCV native library

在使用OpenCV庫編寫Java代碼時，首先需要使用load library（）加載OpenCV的本機庫。加載OpenCV本機庫，如下所示。

// Loading the core library 
System.loadLibrary(Core.NATIVE_LIBRARY_NAME);

Step 2: Instantiate the video capture class

使用本教程前面提到的任何函數實例化Mat類。

// Instantiating the VideoCapture class (camera:: 0) 
VideoCapture capture = new VideoCapture(0);

Step 3: Read the frames

您可以使用VideoCapture類的read（）方法從相機讀取幀。此方法接受類Mat的對象來存儲讀取的幀。

// Reading the next video frame from the camera 
Mat matrix = new Mat(); 
capture.read(matrix);

Example

下面的程序演示如何使用camera捕獲一個幀並使用JavaFX窗口顯示它。它還保存捕獲的幀。

import java.awt.image.BufferedImage;
import java.awt.image.DataBufferByte;
import java.awt.image.WritableRaster;

import java.io.FileNotFoundException;
import java.io.IOException;

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.imgcodecs.Imgcodecs;
import org.opencv.videoio.VideoCapture;

public class CameraSnapshotJavaFX extends Application {
   Mat matrix = null;

   @Override
   public void start(Stage stage) throws FileNotFoundException, IOException {
      // Capturing the snapshot from the camera
      CameraSnapshotJavaFX obj = new CameraSnapshotJavaFX();
      WritableImage writableImage = obj.capureSnapShot();

      // Saving the image
      obj.saveImage();

      // Setting the image view
      ImageView imageView = new ImageView(writableImage);

      // setting the fit height and width of the image view
      imageView.setFitHeight(400);
      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("Capturing an image");

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

      // Displaying the contents of the stage
      stage.show();
   }
   public WritableImage capureSnapShot() {
      WritableImage WritableImage = null;

      // Loading the OpenCV core library
      System.loadLibrary( Core.NATIVE_LIBRARY_NAME );

      // Instantiating the VideoCapture class (camera:: 0)
      VideoCapture capture = new VideoCapture(0);

      // Reading the next video frame from the camera
      Mat matrix = new Mat();
      capture.read(matrix);

      // If camera is opened
      if( capture.isOpened()) {
         // If there is next video frame
         if (capture.read(matrix)) {
            // Creating BuffredImage from the matrix
            BufferedImage image = new BufferedImage(matrix.width(), 
               matrix.height(), BufferedImage.TYPE_3BYTE_BGR);
            
            WritableRaster raster = image.getRaster();
            DataBufferByte dataBuffer = (DataBufferByte) raster.getDataBuffer();
            byte[] data = dataBuffer.getData();
            matrix.get(0, 0, data);
            this.matrix = matrix;
            
            // Creating the Writable Image
            WritableImage = SwingFXUtils.toFXImage(image, null);
         }
      }
      return WritableImage;
   }
   public void saveImage() {
      // Saving the Image
      String file = "E:/OpenCV/chap22/sanpshot.jpg";

      // Instantiating the imgcodecs class
      Imgcodecs imageCodecs = new Imgcodecs();

      // Saving it again 
      imageCodecs.imwrite(file, matrix);
   }
   public static void main(String args[]) {
      launch(args);
   }
}

Output

在執行程序時，您將得到以下輸出。

如果打開指定的路徑，可以看到保存爲jpg文件的同一幀。