OpenCV - 使用相机


在本章中,我们将学习如何使用 OpenCV 使用系统相机捕获帧。org.opencv.videoio包的 VideoCapture 类包含使用相机捕获视频的类和方法让我们一步一步学习如何捕获帧 -

第1步:加载OpenCV原生库

使用 OpenCV 库编写 Java 代码时,您需要做的第一步是使用 loadLibrary ()加载 OpenCV 的本机库。加载 OpenCV 本机库,如下所示。

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

步骤2:实例化视频捕捉类

使用本教程前面提到的任何函数实例化 Mat 类。

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

第三步:读取帧

您可以使用VideoCapture类的read()方法从相机读取帧。此方法接受Mat类的对象来存储读取的帧。

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

例子

以下程序演示了如何使用相机捕获帧并使用 JavaFX 窗口显示它。它还保存捕获的帧。

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);
   }
}

输出

执行程序时,您将得到以下输出。

使用相机捕捉帧

如果打开指定的路径,您可以观察到保存为jpg文件的同一帧。