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捉帧 -
第1步：加载OpenCV本机库
在使用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);
第2步：实例化视频捕获类
使用前面本教程中提到的任何函数来实例化Mat类。
// Instantiating the VideoCapture class (camera:: 0)
VideoCapture capture = new VideoCapture(0);
第3步：读取帧
您可以使用VideoCapture类的read（）方法从相机中读取帧。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);
代码：
1 package com.gitee.dgw.Camera;
2
3 import javafx.application.Application;
4 import javafx.embed.swing.SwingFXUtils;
5 import javafx.scene.Group;
6 import javafx.scene.Scene;
7 import javafx.scene.image.ImageView;
8 import javafx.scene.image.WritableImage;
9 import javafx.stage.Stage;
10 import org.opencv.core.Mat;
11 import org.opencv.imgcodecs.Imgcodecs;
12 import org.opencv.videoio.VideoCapture;
13
14 import java.awt.image.BufferedImage;
15 import java.awt.image.DataBufferByte;
16 import java.awt.image.WritableRaster;
17
18 public class CameraSnapshotJavaFX extends Application {
19
20 static {
21 platformUtils.loadLibraries();
22 }
23 Mat matrix = null;
24
25 @Override
26 public void start(Stage stage) {
27 // Capturing the snapshot from the camera
28 CameraSnapshotJavaFX obj = new CameraSnapshotJavaFX();
29 WritableImage writableImage = obj.capureSnapShot();
30
31 // Saving the image
32 obj.saveImage();
33
34 // Setting the image view
35 ImageView imageView = new ImageView(writableImage);
36
37 // setting the fit height and width of the image view
38 imageView.setFitHeight(400);
39 imageView.setFitWidth(600);
40
41 // Setting the preserve ratio of the image view
42 imageView.setPreserveRatio(true);
43
44 // Creating a Group object
45 Group root = new Group(imageView);
46
47 // Creating a scene object
48 Scene scene = new Scene(root, 600, 400);
49
50 // Setting title to the Stage
51 stage.setTitle("Capturing an image");
52
53 // Adding scene to the stage
54 stage.setScene(scene);
55
56 // Displaying the contents of the stage
57 stage.show();
58 }
59 public WritableImage capureSnapShot() {
60 WritableImage WritableImage = null;
61
62
63 // Instantiating the VideoCapture class (camera:: 0)
64 VideoCapture capture = new VideoCapture(0);
65
66 // Reading the next video frame from the camera
67 Mat matrix = new Mat();
68 capture.read(matrix);
69
70 // If camera is opened
71 if( capture.isOpened()) {
72 // If there is next video frame
73 if (capture.read(matrix)) {
74 // Creating BuffredImage from the matrix
75 BufferedImage image = new BufferedImage(matrix.width(),
76 matrix.height(), BufferedImage.TYPE_3BYTE_BGR);
77
78 WritableRaster raster = image.getRaster();
79 DataBufferByte dataBuffer = (DataBufferByte) raster.getDataBuffer();
80 byte[] data = dataBuffer.getData();
81 matrix.get(0, 0, data);
82 this.matrix = matrix;
83
84 // Creating the Writable Image
85 WritableImage = SwingFXUtils.toFXImage(image, null);
86 }
87 }
88 return WritableImage;
89 }
90 public void saveImage() {
91 // Saving the Image
92 String file = "z://sanpshot.jpg";
93
94 // Instantiating the imgcodecs class
95 Imgcodecs imageCodecs = new Imgcodecs();
96
97 // Saving it again
98 imageCodecs.imwrite(file, matrix);
99 }
100 public static void main(String args[]) {
101 launch(args);
102 }
103
