supervision/docs/how_to/detect_and_annotate.md

6.2 KiB

With Supervision, you can easily annotate predictions obtained from a variety of object detection and segmentation models. This document outlines how to run inference with the YOLOv8 model using the Inference package or the Ultralytics package, load these predictions into Supervision, and annotate the image.

Run Inference

First, you'll need to obtain predictions from your object detection or segmentation model.

=== "Ultralytics"

```python
import cv2
from ultralytics import YOLO

model = YOLO("yolov8n.pt")
image = cv2.imread("image.jpg")
results = model(image)[0]
```

=== "Inference"

To run inference, you will need a [free Roboflow API key]().

```python
import cv2
from inference.models.utils import get_roboflow_model

model = get_roboflow_model(model_id="yolov8n-640", api_key="YOUR_ROBOFLOW_API_KEY")
image = cv2.imread("image.jpg")
results = model.infer(image)[0]
```

Load Predictions into Supervision

Now that we have predictions from a model, we can load them into Supervision.

=== "Ultralytics"

We can do so using the [`sv.Detections.from_ultralytics`](https://supervision.roboflow.com/detection/core/#supervision.detection.core.Detections.from_ultralytics) method, which accepts model results from both detection and segmentation models.

```python
import cv2
from ultralytics import YOLO
import supervision as sv

model = YOLO("yolov8n.pt")
image = cv2.imread("image.jpg")
results = model(image)[0]
detections = sv.Detections.from_ultralytics(results)
```

=== "Inference"

We can do so using the [`sv.Detections.from_inference`](https://supervision.roboflow.com/detection/core/#supervision.detection.core.Detections.from_inference) method, which accepts model results from both detection and segmentation models.

```python
import cv2
from inference.models.utils import get_roboflow_model
import supervision as sv

model = get_roboflow_model(model_id="yolov8n-640", api_key="YOUR_ROBOFLOW_API_KEY")
image = cv2.imread("image.jpg")
results = model.infer(image)[0]
detections = sv.Detections.from_inference(results)
```

You can conveniently load predictions from other computer vision frameworks and libraries using:

Annotate Image

Finally, we can annotate the image with the predictions. Since we are working with an object detection model, we will use the sv.BoundingBoxAnnotator and sv.LabelAnnotator classes. If you are running the segmentation model sv.MaskAnnotator is a drop-in replacement for sv.BoundingBoxAnnotator that will allow you to draw masks instead of boxes.

=== "Ultralytics"

```python
import cv2
from ultralytics import YOLO
import supervision as sv

model = YOLO("yolov8n.pt")
image = cv2.imread("image.jpg")
results = model(image)[0]
detections = sv.Detections.from_ultralytics(results)

bounding_box_annotator = sv.BoundingBoxAnnotator()
label_annotator = sv.LabelAnnotator()

labels = [
    results.names[class_id]
    for class_id
    in detections.class_id
]

annotated_image = bounding_box_annotator.annotate(
    scene=image, detections=detections)
annotated_image = label_annotator.annotate(
    scene=annotated_image, detections=detections, labels=labels)
```

=== "Inference"

```python
import cv2
from inference.models.utils import get_roboflow_model
import supervision as sv

model = get_roboflow_model(model_id="yolov8n-640", api_key="YOUR_ROBOFLOW_API_KEY")
image = cv2.imread("image.jpg")
results = model.infer(image)[0]
detections = sv.Detections.from_inference(results)

bounding_box_annotator = sv.BoundingBoxAnnotator()
label_annotator = sv.LabelAnnotator()

labels = [
    results.names[class_id]
    for class_id
    in detections.class_id
]

annotated_image = bounding_box_annotator.annotate(
    scene=image, detections=detections)
annotated_image = label_annotator.annotate(
    scene=annotated_image, detections=detections, labels=labels)
```

Predictions plotted on an image

Display Annotated Image

To display the annotated image in Jupyter Notebook or Google Colab, use the sv.plot_image function.

sv.plot_image(annotated_image)