Taking a Snapshot from System Camera using OpenCV in Java


OpenCV (Open Source Computer Vision Library) is an open-source computer vision and machine learning software library. It contains more than 2500 optimized algorithms, which are extensively used in real-time applications.

Java provides bindings to OpenCV via the JavaCV library, allowing Java developers to leverage OpenCV's capabilities in their applications. One such application is capturing images from a webcam.


To follow along, you need to have the following −

  • OpenCV installed on your system.

  • JavaCV, a wrapper for OpenCV in Java.

Capturing a Snapshot using OpenCV

To capture a snapshot, we need to create an instance of the VideoCapture class, which represents a video capturing device. We can then use the read method to capture a frame from the video feed.


Let's take a look at an example −

import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.videoio.VideoCapture;
import org.opencv.imgcodecs.Imgcodecs;

public class Main {
   static { System.loadLibrary(Core.NATIVE_LIBRARY_NAME); }
   public static void main(String[] args) {

      // Create a VideoCapture object
      VideoCapture camera = new VideoCapture(0);
      // Check if camera opened successfully
         System.out.println("Error: Camera not accessible");
      // Capture a new frame
      Mat frame = new Mat();
      // Save the frame as an image
      Imgcodecs.imwrite("snapshot.png", frame);
      // Release the camera


In the above code, we first load the OpenCV library.

We then create a VideoCapture object for the default camera (index 0). If you have multiple cameras and want to use a different one, you can specify its index when creating the VideoCapture object.

We check if the camera opened successfully using the isOpened method. If the camera isn't accessible, we print an error message and return from the main method.

Next, we capture a frame from the camera using the read method and store it in a Mat object. Mat (short for Matrix) is the primary image structure in OpenCV and is used to store pixel data.

We save the captured frame as an image using the imwrite method from the Imgcodecs class, giving it the name "snapshot.png".

Finally, we release the camera using the release method to free up resources.

When you run this program, it will capture a single frame from your webcam and save it as "snapshot.png" in your project directory.


Capturing images from a webcam in Java using OpenCV is a straightforward process, and it opens up a wealth of opportunities for more complex applications, such as face recognition, motion detection, and more. Understanding how to work with the OpenCV library in Java provides a strong foundation for diving into computer vision and image processing.

Updated on: 15-May-2023


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