scripts/extract.py

"""Extract gear digit crops from a racing video.

Usage:
    uv run python scripts/extract.py <video_path> <source_name> <x> <y> <w> <h> [--fps 5]

Example:
    uv run python scripts/extract.py /path/to/video.mp4 sebring-tobi-lap6 1440 780 90 105
    uv run python scripts/extract.py /path/to/video.mp4 paul-ricard-alpine 685 320 55 55

Outputs:
    raw/<source_name>/unlabeled/frame_XXXXX.png  - individual crops
    composites/<source_name>/unlabeled.png        - contact sheet for labeling
"""

import argparse
import os
import subprocess
import sys
from PIL import Image


def main():
    parser = argparse.ArgumentParser(description="Extract gear crops from racing video")
    parser.add_argument("video", help="Path to video file")
    parser.add_argument("source", help="Source name (e.g. sebring-tobi-lap6)")
    parser.add_argument("x", type=int, help="Crop X offset")
    parser.add_argument("y", type=int, help="Crop Y offset")
    parser.add_argument("w", type=int, help="Crop width")
    parser.add_argument("h", type=int, help="Crop height")
    parser.add_argument("--fps", type=int, default=5, help="Extraction frame rate (default: 5)")
    args = parser.parse_args()

    out_dir = f"raw/{args.source}/unlabeled"
    comp_dir = f"composites/{args.source}"
    os.makedirs(out_dir, exist_ok=True)
    os.makedirs(comp_dir, exist_ok=True)

    # Extract with ffmpeg
    print(f"Extracting from {args.video}")
    print(f"  Crop: ({args.x}, {args.y}, {args.w}×{args.h}) at {args.fps}fps")
    cmd = [
        "ffmpeg", "-y",
        "-i", args.video,
        "-vf", f"crop={args.w}:{args.h}:{args.x}:{args.y}",
        "-r", str(args.fps),
        f"{out_dir}/frame_%05d.png",
    ]
    subprocess.run(cmd, capture_output=True)

    # Build composite contact sheet
    frames = sorted(f for f in os.listdir(out_dir) if f.endswith(".png"))
    print(f"  Extracted {len(frames)} frames")

    cols = 40
    cell = 40
    rows = (len(frames) + cols - 1) // cols
    sheet = Image.new("L", (cols * cell, rows * cell), 0)
    for idx, f in enumerate(frames):
        img = Image.open(os.path.join(out_dir, f)).convert("L").resize((cell, cell))
        r, c = idx // cols, idx % cols
        sheet.paste(img, (c * cell, r * cell))
    
    comp_path = f"{comp_dir}/unlabeled.png"
    sheet.save(comp_path)
    print(f"  Composite: {comp_path} ({cols}×{rows})")
    print()
    print(f"Next: create labels/{args.source}.csv with columns: start,end,label")
    print(f"  Each row is a frame range (0-indexed) and its gear digit.")
    print(f"  Then run: uv run python scripts/build_dataset.py")


if __name__ == "__main__":
    main()