The roboRIO can forward video to the driver station to allow a human driver to see while driving even when line of sight is blocked. Even better, we can process the video, either to assist the human driver (e.g. by placing cross hairs where a shooter is pointed) or by automatically finding a game piece of target during autonomous operation.

Most video processing is done using the free open-source library: OpenCV which is included with WPILib.

The example Robot.java below displays the video from a USB camera on the dashboard and creates a red rectangular overlay to assist the driver:

package frc.robot;

import org.opencv.core.Mat;
import org.opencv.imgproc.Imgproc;
import org.opencv.core.Scalar;
import org.opencv.core.Point;

import edu.wpi.cscore.CvSink;
import edu.wpi.cscore.CvSource;
import edu.wpi.cscore.UsbCamera;
import edu.wpi.first.cameraserver.*;
import edu.wpi.first.wpilibj.TimedRobot;

public class Robot extends TimedRobot {
    
    public void robotInit() {
            // do camera processing in its own thread so if anything goes wrong,
            // we don't take down the entire robot
            new Thread(() -> {
                // get a handle to the camera server that accesses the USB camera
                UsbCamera camera = CameraServer.getInstance().startAutomaticCapture();
                camera.setResolution(640, 480);
 
                // CvSink receives video from the camera               
                CvSink cvSink = CameraServer.getInstance().getVideo();
                // CvSource sends video stream (named "Rectangle") to the smart dashboard
                CvSource outputStream = CameraServer.getInstance().putVideo("Rectangle", 640, 480);
                
                // We store video frames in a Mat for processing
                Mat mat = new Mat();
                
                while(!Thread.interrupted()) {
                  // grab a frame from the video stream
                  if (cvSink.grabFrame(mat) == 0) {
                    outputStream.notifyError(cvSink.getError());
                    // skip the rest of the current iteration
                    continue;
                  }
                  // Put a red rectangle on the image
                  Imgproc.rectangle(mat,                                    // mat to operate on
                                    new Point(160,120), new Point(480,360), // rectangle coords
                                    new Scalar(0,0,255),                    // OpenCV uses BGR
                                    5);                                     // line thickness
                  // Give the output stream a new image to display
                  outputStream.putFrame(mat);
              }
            }).start();
    }
}