# Open Robotics Darknet ROS

This is a ROS 2 wrapper around [darknet](https://pjreddie.com/darknet), an open source neural network framework.

![Example image with bounding boxes created using darknet and the yolov3-tiny network](doc/example_darknet_yolov3-tiny.png)

## DetectorNode

This node can run object detectors like [YOLOv3](https://pjreddie.com/darknet/yolo/) on images.

### Subscribers

* `~/images` (type `sensor_msgs/msg/Image`) - Input mages to feed to the detector

### Publishers

* `~/detections` (type `vision_msgs/msg/Detection2DArray`) - Objects detected in an image (if any)

### Parameters

* `network.config` - a path to a file describing a darknet detector network
* `network.weights` - a path to a file with weights for the given network
* `network.class_names` - a path to a file with names of classes the network can detect (1 per line)
* `detection.threshold` - Minimum probability of a detection to be published
* `detection.nms_threshold` - Non-maximal Suppression threshold - controls filtering of overlapping boxes

### Example

Download `YOLOv3-tiny`.

```
wget https://raw.githubusercontent.com/pjreddie/darknet/f86901f6177dfc6116360a13cc06ab680e0c86b0/cfg/yolov3-tiny.cfg
wget https://pjreddie.com/media/files/yolov3-tiny.weights
wget https://raw.githubusercontent.com/pjreddie/darknet/c6afc7ff1499fbbe64069e1843d7929bd7ae2eaa/data/coco.names
```

Save the following as `detector_node_params.yaml`

```yaml
/**:
  ros__parameters:
    network:
      config: "./yolov3-tiny.cfg"
      weights: "./yolov3-tiny.weights"
      class_names: "./coco.names"
    detection:
      threshold: 0.25
      nms_threshold: 0.45
```

Then run the node.

```
ros2 run openrobotics_darknet_ros detector_node __params:=detector_node_params.yaml
```

The node is now running.
Publish images on `~/images` to get the node to detect objects.