Vision Examples¶

Working examples for the vision module's camera drivers and image processing.

All scripts use argparse flags (not --ros-args -p). Run with python3 <script>.py [flags]. Some scripts are also installed as ROS 2 executables (ros2 run nectar <script>.py -- [flags]): camera_example.py, depth_example.py, t265_example.py, collect_photos.py. Use python3 for optical_flow_example.py (not installed as an executable).

Camera Example¶

Camera capture using ImageHandler with configurable backends.

Usage¶

Run with the default webcam, or pass any --camera-type from Supported Camera Types; add --no-show to run headless.

python3 camera_example.py
python3 camera_example.py --camera-type realsense

Arguments¶

Supported Camera Types¶

Depth Example¶

Demonstrates depth camera usage with interactive distance measurement.

Usage¶

Features¶

• RGB Display: Color image with crosshair at selected pixel
• Depth Colormap: Plasma colormap visualization (0.1m - 3.0m range)
• Interactive Selection: Click on color image to select measurement point
• Distance Display: Real-time distance in meters at selected pixel

Keyboard Controls¶

T265 Tracking¶

RealSense T265 tracking camera pose/odometry, either through the direct SDK or via ROS topics.

Runs in direct-SDK mode by default; see the arguments below for ROS mode and the depth toggle.

python3 t265_example.py
python3 t265_example.py --mode ros

Optical Flow¶

Sparse (Lucas-Kanade) or dense (Farneback) optical flow. With --focal/--altitude it also decodes angular rate (rad/s) and horizontal velocity (m/s), like the ArduPilot OPTICAL_FLOW pipeline.

Photo Collection¶

Captures frames at a configurable interval and saves them to an organized directory structure. Useful for building training datasets — fly the drone via RC or the Nectar interface while this node records frames.

Usage¶

Arguments¶

Output Structure¶

~/hook_photos/
├── flight_01_low_alt/
│   ├── frame_00001.jpg
│   ├── frame_00002.jpg
│   └── ...
├── flight_02_high_alt/
│   ├── frame_00001.jpg
│   └── ...
└── 20260416_143022/          # auto-named when run_name is empty
    └── ...

Troubleshooting¶

Camera Not Found¶

ValueError: Unknown camera source type: xyz

Check registered camera types:

from nectar.vision.camera import CameraFactory
# Registered: webcam, opencv, realsense, t265, oakd, c920, imx219, ros, ros_depth, file

RealSense Import Error¶

RuntimeError: pyrealsense2 is not installed

Install librealsense and realsense-ros (builds matching pyrealsense2 from source):

make realsense
# T265 (Humble only): LIBREALSENSE_VERSION=v2.53.1 REALSENSE_ROS_TAG=4.51.1 make realsense

Or use ROS topic mode (realsense_ros / ros_depth) with realsense2_camera already running.

OAK-D Import Error¶

ModuleNotFoundError: No module named 'depthai'

Install DepthAI:

pip install depthai

Low FPS / Frame Drops¶

Adjust buffer and threading settings:

config = OpenCVConfig(
    buffer_size=2,    # Increase if dropping frames
    threaded=True,    # Enable background capture
)

Display Not Working¶

cv2.error: The function is not implemented

OpenCV headless build. Options:

• Install opencv-python instead of opencv-python-headless
• Disable display: show_result=None

Dependencies¶