How can i add a line counter in traffic analysis example with classes counting separately

[hugoles]

Search before asking

• I have searched the Supervision issues and found no similar feature requests.

Question

I have been using the traffic_analysis example, but when trying to implement a separate counter for each class (car, bus, van, truck), I realized that it wouldn't be the same in other projects, mainly because the tracker_id seems to unify everything into one class. How could I implement this?

Additional

No response

[github-actions[bot]]

Hello there, thank you for opening an Issue ! 🙏🏻 The team was notified and they will get back to you asap.

[SkalskiP]

Hi, @hugoles 👋🏻 Let me convert this issue into discussion and move it into the Q&A section.

[SkalskiP]

Currently, LineZone does not offer object counting by class. To achieve this result, you must create multiple LineZone objects - a separate one for each category. Filter detections by category and trigger LineZones separately. A minimal example is below.👇🏻

This will only work well if the categories provided by your model are stable.

import supervision as sv
from ultralytics import YOLO

# indexes of coco classes related to car, bus, truck
CLASS_IDS = [2, 5, 7]
SOURCE_PATH = ...
START = sv.Point(...)
END = sv.Point(...)

line_zones = {
    class_id: sv.LineZone(start=START, end=END)
    for class_id
    in CLASS_IDS
}

frame_generator = sv.get_video_frames_generator(source_path='source.mp4')

for frame in frame_generator:

    results = self.model(frame)[0]
    detections = sv.Detections.from_ultralytics(results) 
    detections = self.tracker.update_with_detections(detections)

    for class_id in CLASS_IDS:
        class_detections = detections[detections.class_id == class_id]
        line_zones[CLASS_IDS].trigger(class_detections)

[hugoles]

@SkalskiP I really appreciate your help, even though I may not be using this code directly. It has helped me gain a better understanding of the code. Here's what I've accomplished so far: #562 (comment)