scripts/prepare.py

#!/usr/bin/env python
"""
Downloads and extracts additional data from the Cityscapes dataset, moving the
required files to (existing) data directory.
"""

import tempfile
from tqdm import tqdm
import os
import re
from pathlib import Path
import shutil
import zipfile
import argparse
import pandas as pd

from cityscapesscripts.download import downloader

PACKAGE_TO_VARIABLE = {
    "vehicle_sequence": "vehicle",
    "timestamp_sequence": "timestamp",
    "leftImg8bit_sequence_trainvaltest": "image",
    "camera_trainvaltest": "camera",
}


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(
        description="Download and extract the Cityscapes dataset."
    )
    parser.add_argument(
        "manifest_file",
        type=Path,
        help="Path to the manifest file (e.g., 'manifest.csv').",
    )
    parser.add_argument(
        "downloads_dir",
        type=Path,
        help="Path to the directory where ZIP files are/will be stored (e.g., 'downloads').",
    )
    parser.add_argument(
        "data_dir",
        type=Path,
        help="Path to the directory where extracted files should be moved (e.g., 'data').",
    )
    return parser.parse_args()


def read_manifest(manifest_file: str) -> pd.DataFrame:
    """
    Read the manifest file and return a DataFrame.
    """
    df = pd.read_csv(manifest_file, index_col="primary_key")
    assert "split" in df.columns, "Missing 'split' column in manifest."
    assert "sequence" in df.columns, "Missing 'sequence' column in manifest."
    assert "frame" in df.columns, "Missing 'frame' column in manifest."
    return df


def download_files(downloads_dir: str, zip_files: list[str]):
    if not zip_files:
        print("No files to download.")
        return

    session = downloader.login()

    downloader.download_packages(
        session=session,
        package_names=zip_files,
        destination_path=downloads_dir,
        resume=True,
    )


def unzip_and_move(
    pkg: str,
    downloads_dir: Path,
    data_dir: Path,
    manifest: pd.DataFrame,
    source_split: str,
):
    """
    Unzip, rename, and move the requested split files for a single package.
    """
    zip_path = downloads_dir / f"{pkg}.zip"
    pkg_type = PACKAGE_TO_VARIABLE[pkg]

    re_name = re.compile(r"([^_]*_[^_]*_[^_]*)_.*")

    if not zip_path.is_file():
        print(f"Warning: ZIP file not found => {zip_path}. Skipping...")
        return

    print(f"Processing: {zip_path}")

    with tempfile.TemporaryDirectory() as td, zipfile.ZipFile(zip_path, "r") as zf:
        names = zf.namelist()
        for member in tqdm(names):
            if f"/{source_split}/" not in member:
                continue

            # Extract the file and get its new path in the temporary directory
            res_path = Path(zf.extract(member, td))

            if res_path.is_dir():
                continue

            # Read the manifest to find the specification of this sample
            primary_key = re_name.sub(r"\1", res_path.stem)
            sample = manifest.loc[primary_key]

            # Build the new path
            new_path = data_dir / sample["split"]

            if pkg_type in {"camera"}:
                # New name is: split/<sequence>.<type>.<ext>
                new_path /= "{:06d}.{:s}{:s}".format(
                    sample["sequence"], pkg_type, res_path.suffix
                )
            else:
                # New name is: split/<sequence>/<frame>.<type>.<ext>
                new_path /= "{:06d}".format(sample["sequence"])
                new_path /= "{:06d}.{:s}{:s}".format(
                    sample["frame"], pkg_type, res_path.suffix
                )
            if new_path.is_file():
                continue
            new_path.parent.mkdir(parents=True, exist_ok=True)

            shutil.move(res_path, new_path)


def main():
    args = parse_args()

    # Create directories if not exists
    for dir in (args.downloads_dir, args.data_dir):
        os.makedirs(dir, exist_ok=True)

    # Read the manifest file
    manifest = read_manifest(args.manifest_file)

    # Prepare list of package zip files
    packages = list(PACKAGE_TO_VARIABLE.keys())
    zip_files = [f"{pkg}.zip" for pkg in packages]

    # Filter out existing ZIPs
    download_list = []
    for zf in zip_files:
        zf_path = os.path.join(args.downloads_dir, zf)
        if os.path.isfile(zf_path):
            print(f"Already downloaded: {zf_path}")
        else:
            print(f"Needs to be downloaded: {zf_path}")
            download_list.append(zf)

    # Download missing ZIP files using csDownload directly
    download_files(args.downloads_dir, download_list)

    # Unzip, rename, and move each package
    for pkg in packages:
        unzip_and_move(pkg, args.downloads_dir, args.data_dir, manifest, "val")

    print(f"Successfully processed: {packages}")


if __name__ == "__main__":
    main()