RaspiLedClient.java

import java.awt.*;
import java.awt.image.*;
import java.io.*;
import java.net.*; 

public class RaspiLedClient {

    public static void main(String[] args) throws Exception{
        //screen size
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        int screenW     = (int)screenSize.getWidth();
        int screenH     = (int)screenSize.getHeight();

        int pixelSkip = 1;
        String hex;
        //variables for taking the screenshot
        int[] screenData;
        BufferedImage screenshot;
        Robot bot;
        Rectangle dispBounds = new Rectangle(new Dimension(screenW,screenH));

        String restPort = "42069";
        int udpPort = 1337;
        
        if (args.length == 3){
            restPort = args[1];
            udpPort = Integer.parseInt(args[2]);
        }else if (args.length != 1){
            System.out.println("Usage:\njava RaspiLedClient <host>\njava RaspiLedClient <host> <rest_port> <udp_port>");
            System.exit(1);
        }
        
        InetAddress ipAddress = InetAddress.getByName(args[0]);

        
        String urlString = new StringBuilder("http:/").append(ipAddress).append(":").append(restPort).append("/set/stream").toString();
        URL streamUrl = new URL(urlString);
        
        try{
            HttpURLConnection con = (HttpURLConnection) streamUrl.openConnection();
            con.setRequestMethod("GET");
            if (con.getResponseCode() != 200){
                System.out.println("ERROR: Stream mode could not be started on backend.");
                System.exit(1);
            }
        }catch(ConnectException e){
            System.out.println("ERROR: Backend unavailable.");
            System.exit(1);
        }
        
        DatagramSocket clientSocket = new DatagramSocket();
                
        try   {
            bot = new Robot();
            while(true){
            screenshot = bot.createScreenCapture(dispBounds);
            screenData = ((DataBufferInt)screenshot.getRaster().getDataBuffer()).getData();
            hex = getAvgScreenColor(screenW, screenH, pixelSkip, screenData);
            System.out.println("RGB = " + hex);
            clientSocket.send(new DatagramPacket(hex.getBytes(), 6, ipAddress, udpPort));
          }
      	}
      	catch (AWTException e)  {
      		System.out.println("Robot class not supported by your system!");
      		System.exit(0);
      	}

        clientSocket.close();
    }

    private static String getAvgScreenColor(int screenW, int screenH, int pixelSkip, int[] screenData){
      int pixel;
      int r = 0;
      int g = 0;
      int b = 0;
      int[] col = new int[3];
      String hex;

      for(int i = 0; i < screenH; i += pixelSkip){
        for(int j = 0; j < screenW; j += pixelSkip){
          pixel = screenData[ i*screenW + j ];
          r += 0xff & (pixel>>16);
          g += 0xff & (pixel>>8 );
          b += 0xff &  pixel;
        }
      }

      col[0]  = r / (screenH/pixelSkip * screenW/pixelSkip);
      col[1]  = g / (screenH/pixelSkip * screenW/pixelSkip);
      col[2]  = b / (screenH/pixelSkip * screenW/pixelSkip);
      hex = String.format("%02x%02x%02x", col[0], col[1], col[2]);
      return hex;
    }

}