Add Photonlib (#231)

Merges Photonlib into Photonvision, along with the Photonlib code examples. Also creates a new PhotonTargeting library teams can depend on.

photon-lib/src/main/native/include/photonlib/PhotonTrackedTarget.h

@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) Photon Vision.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <cstddef>
+#include <string>
+#include <vector>
+
+#include <frc/geometry/Transform2d.h>
+
+#include "photonlib/Packet.h"
+
+namespace photonlib {
+/**
+ * Represents a tracked target within a pipeline.
+ */
+class PhotonTrackedTarget {
+ public:
+  /**
+   * Constructs an empty target.
+   */
+  PhotonTrackedTarget() = default;
+
+  /**
+   * Constructs a target.
+   * @param yaw The yaw of the target.
+   * @param pitch The pitch of the target.
+   * @param area The area of the target.
+   * @param skew The skew of the target.
+   * @param pose The camera-relative pose of the target.
+   */
+  PhotonTrackedTarget(double yaw, double pitch, double area, double skew,
+                      const frc::Transform2d& pose);
+
+  /**
+   * Returns the target yaw (positive-left).
+   * @return The target yaw.
+   */
+  double GetYaw() const { return yaw; }
+
+  /**
+   * Returns the target pitch (positive-up)
+   * @return The target pitch.
+   */
+  double GetPitch() const { return pitch; }
+
+  /**
+   * Returns the target area (0-100).
+   * @return The target area.
+   */
+  double GetArea() const { return area; }
+
+  /**
+   * Returns the target skew (counter-clockwise positive).
+   * @return The target skew.
+   */
+  double GetSkew() const { return skew; }
+
+  /**
+   * Returns the pose of the target relative to the robot.
+   * @return The pose of the target relative to the robot.
+   */
+  frc::Transform2d GetCameraRelativePose() const { return cameraToTarget; }
+
+  bool operator==(const PhotonTrackedTarget& other) const;
+  bool operator!=(const PhotonTrackedTarget& other) const;
+
+  friend Packet& operator<<(Packet& packet, const PhotonTrackedTarget& target);
+  friend Packet& operator>>(Packet& packet, PhotonTrackedTarget& target);
+
+ private:
+  double yaw = 0;
+  double pitch = 0;
+  double area = 0;
+  double skew = 0;
+  frc::Transform2d cameraToTarget;
+};
+}  // namespace photonlib