Python Image Converter Project

"""Convert a local image to PNG, JPEG, WEBP, BMP, or TIFF with Pillow."""

from __future__ import annotations

import argparse
from pathlib import Path

from PIL import Image, ImageOps, UnidentifiedImageError


FORMATS = {
    ".png": "PNG",
    ".jpg": "JPEG",
    ".jpeg": "JPEG",
    ".webp": "WEBP",
    ".bmp": "BMP",
    ".tif": "TIFF",
    ".tiff": "TIFF",
}


def flatten_transparency(image: Image.Image) -> Image.Image:
    """Place transparent pixels on white before saving as JPEG or BMP."""
    rgba = image.convert("RGBA")
    background = Image.new("RGBA", rgba.size, "white")
    background.alpha_composite(rgba)
    return background.convert("RGB")


def convert_image(source: Path, destination: Path) -> tuple[int, int]:
    if not source.is_file():
        raise ValueError(f"Input image does not exist: {source}")
    if source.resolve() == destination.resolve():
        raise ValueError("Choose a different output filename so the source is preserved.")

    output_format = FORMATS.get(destination.suffix.lower())
    if output_format is None:
        supported = ", ".join(sorted(FORMATS))
        raise ValueError(f"Unsupported output extension. Choose one of: {supported}")

    destination.parent.mkdir(parents=True, exist_ok=True)
    with Image.open(source) as opened:
        opened.seek(0)
        image = ImageOps.exif_transpose(opened)
        image.load()

        if output_format in {"JPEG", "BMP"}:
            image = flatten_transparency(image)
        elif image.mode not in {"1", "L", "LA", "P", "RGB", "RGBA", "CMYK"}:
            image = image.convert("RGBA")

        save_options = {"quality": 90, "optimize": True} if output_format in {"JPEG", "WEBP"} else {}
        image.save(destination, format=output_format, **save_options)
        return image.size


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(description="Convert an image based on the output extension.")
    parser.add_argument("source", type=Path)
    parser.add_argument("destination", type=Path)
    return parser.parse_args()


def main() -> None:
    args = parse_args()
    try:
        width, height = convert_image(args.source, args.destination)
    except (ValueError, OSError, UnidentifiedImageError) as error:
        raise SystemExit(f"Conversion failed: {error}") from error
    print(f"Created {args.destination} ({width} x {height} pixels).")


if __name__ == "__main__":
    main()