id: "ee4e0037-ac33-4813-aad9-0a950ddcc6c2" name: "YOLOv5 Object Detection with ROI Masking and GPU Support" description: "Implement real-time object detection using YOLOv5 constrained to a specific Region of Interest (ROI) polygon, utilizing GPU acceleration and the supervision library for annotation." version: "0.1.0" tags:

• "yolo"
• "computer-vision"
• "roi"
• "gpu"
• "python"
• "opencv" triggers:
• "yolov5 roi masking"
• "detect objects in polygon area"
• "yolov5 gpu inference"
• "supervision library yolo"

YOLOv5 Object Detection with ROI Masking and GPU Support

Implement real-time object detection using YOLOv5 constrained to a specific Region of Interest (ROI) polygon, utilizing GPU acceleration and the supervision library for annotation.

Prompt

Role & Objective

Act as a Computer Vision Engineer. Write Python code to perform real-time object detection using YOLOv5, constrained to a specific Region of Interest (ROI) defined by a polygon. The code must run on GPU if available.

Operational Rules & Constraints

1. Model Loading: Load YOLOv5 via torch.hub.load('ultralytics/yolov5', 'yolov5s6', device=device).
2. Device Selection: Automatically select CUDA if available: device = 'cuda' if torch.cuda.is_available() else 'cpu'.
3. ROI Definition: Define the ROI as a numpy array of integer coordinates (e.g., np.array([[x1,y1], [x2,y2], ...], dtype=np.int32)).
4. Masking Logic:
   • Create a black mask matching frame dimensions.
   • Fill the ROI polygon with white (255, 255, 255).
   • Apply cv2.bitwise_and to mask the frame.
5. Inference: Run model inference on the masked frame.
6. Filtering: Filter detections to keep only class ID 0 (person) with confidence > 0.5.
7. Annotation: Use supervision.BoxAnnotator to draw boxes on the original (unmasked) frame.
8. Visualization: Draw the ROI polygon outline on the annotated frame and display the count of detections.

Communication & Style Preferences

Provide the complete, runnable Python script including imports and the main execution loop.

Triggers

• yolov5 roi masking
• detect objects in polygon area
• yolov5 gpu inference
• supervision library yolo