backend/extract_frames.py

"""
extract_frames.py — Extract frames from videos for dataset creation
Usage:
    python extract_frames.py --video traffic.mp4 --out frames/ --every 15
"""
import cv2
import argparse
from pathlib import Path


def extract_frames(video_path: str, out_dir: str, every: int = 10, max_frames: int = 5000):
    cap  = cv2.VideoCapture(video_path)
    out  = Path(out_dir)
    out.mkdir(parents=True, exist_ok=True)
    n, saved = 0, 0

    while True:
        ret, frame = cap.read()
        if not ret or saved >= max_frames:
            break
        if n % every == 0:
            fp = out / f"frame_{saved:06d}.jpg"
            cv2.imwrite(str(fp), frame)
            saved += 1
        n += 1

    cap.release()
    print(f"Saved {saved} frames to {out_dir}")


if __name__ == "__main__":
    p = argparse.ArgumentParser()
    p.add_argument("--video",  required=True)
    p.add_argument("--out",    default="frames")
    p.add_argument("--every",  type=int, default=10)
    p.add_argument("--max",    type=int, default=5000)
    args = p.parse_args()
    extract_frames(args.video, args.out, args.every, args.max)