Main.java

// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.

package org.wpilib;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import org.wpilib.networktables.NetworkTableInstance;
import org.wpilib.vision.camera.VideoSource;
import org.wpilib.vision.stream.CameraServer;

/*
  JSON format:
  {
      "team": <team number>,
      "ntmode": <"client" or "server", "client" if unspecified>
      "cameras": [
          {
              "name": <camera name>
              "path": <path, e.g. "/dev/video0">
              "pixel format": <"MJPEG", "YUYV", etc>   // optional
              "width": <video mode width>              // optional
              "height": <video mode height>            // optional
              "fps": <video mode fps>                  // optional
              "brightness": <percentage brightness>    // optional
              "white balance": <"auto", "hold", value> // optional
              "exposure": <"auto", "hold", value>      // optional
              "properties": [                          // optional
                  {
                      "name": <property name>
                      "value": <property value>
                  }
              ]
          }
      ]
  }
*/

public final class Main {
  private static String configFile = "/boot/CameraServerConfig.json";

  public static class CameraConfig {
    public String name;
    public String path;
    public JsonObject config;
  }

  private static int team;
  private static boolean server;
  private static List<CameraConfig> cameras = new ArrayList<>();

  private Main() {}

  /** Report parse error. */
  public static void parseError(String str) {
    System.err.println("config error in '" + configFile + "': " + str);
  }

  /** Read single camera configuration. */
  public static boolean readCameraConfig(JsonObject config) {
    CameraConfig cam = new CameraConfig();

    // name
    JsonElement nameElement = config.get("name");
    if (nameElement == null) {
      parseError("could not read camera name");
      return false;
    }
    cam.name = nameElement.getAsString();

    // path
    JsonElement pathElement = config.get("path");
    if (pathElement == null) {
      parseError("camera '" + cam.name + "': could not read path");
      return false;
    }
    cam.path = pathElement.getAsString();

    cam.config = config;

    cameras.add(cam);
    return true;
  }

  /** Read configuration file. */
  public static boolean readConfig() {
    // parse file
    JsonElement top;
    try {
      top = JsonParser.parseReader(Files.newBufferedReader(Paths.get(configFile)));
    } catch (IOException ex) {
      System.err.println("could not open '" + configFile + "': " + ex);
      return false;
    }

    // top level must be an object
    if (!top.isJsonObject()) {
      parseError("must be JSON object");
      return false;
    }
    JsonObject obj = top.getAsJsonObject();

    // team number
    JsonElement teamElement = obj.get("team");
    if (teamElement == null) {
      parseError("could not read team number");
      return false;
    }
    team = teamElement.getAsInt();

    // ntmode (optional)
    if (obj.has("ntmode")) {
      String str = obj.get("ntmode").getAsString();
      if ("client".equalsIgnoreCase(str)) {
        server = false;
      } else if ("server".equalsIgnoreCase(str)) {
        server = true;
      } else {
        parseError("could not understand ntmode value '" + str + "'");
      }
    }

    // cameras
    JsonElement camerasElement = obj.get("cameras");
    if (camerasElement == null) {
      parseError("could not read cameras");
      return false;
    }
    JsonArray cameras = camerasElement.getAsJsonArray();
    for (JsonElement camera : cameras) {
      if (!readCameraConfig(camera.getAsJsonObject())) {
        return false;
      }
    }

    return true;
  }

  /** Start running the camera. */
  public static void startCamera(CameraConfig config) {
    System.out.println("Starting camera '" + config.name + "' on " + config.path);
    VideoSource camera = CameraServer.startAutomaticCapture(config.name, config.path);

    Gson gson = new GsonBuilder().create();

    camera.setConfigJson(gson.toJson(config.config));
  }

  /** Main. */
  public static void main(String... args) {
    if (args.length > 0) {
      configFile = args[0];
    }

    // read configuration
    if (!readConfig()) {
      return;
    }

    // start NetworkTables
    NetworkTableInstance ntinst = NetworkTableInstance.getDefault();
    if (server) {
      System.out.println("Setting up NetworkTables server");
      ntinst.startServer();
    } else {
      System.out.println("Setting up NetworkTables client for team " + team);
      ntinst.setServerTeam(team);
      ntinst.startClient("multicameraserver");
    }

    // start cameras
    for (CameraConfig camera : cameras) {
      startCamera(camera);
    }

    // loop forever
    for (; ; ) {
      try {
        Thread.sleep(10000);
      } catch (InterruptedException ex) {
        return;
      }
    }
  }
}