Convert png to ico image with multiple sizes.

png2ico.py

#!/usr/bin/env python3

# File: png2ico.py
# Author: Hadi Cahyadi <cumulus13@gmail.com>
# Date: 2025-12-22
# Description: Convert png to ico image with multiple sizes.
# License: MIT


from pathlib import Path
from PIL import Image
import sys

# All common icon sizes
ALL_SIZES = [16, 20, 24, 32, 40, 48, 64, 72, 96, 128, 256, 512]

def make_square(img: Image.Image, size: int):
    """Resize and pad to a transparent square"""
    img = img.convert("RGBA")
    w, h = img.size
    scale = min(size / w, size / h)
    new_w, new_h = int(w * scale), int(h * scale)
    resized = img.resize((new_w, new_h), Image.LANCZOS)
    canvas = Image.new("RGBA", (size, size), (0, 0, 0, 0))
    canvas.paste(resized, ((size - new_w)//2, (size - new_h)//2), resized)
    return canvas

def png_to_icos(png_path: Path):
    with Image.open(png_path) as img:
        img = img.convert("RGBA")
        base = png_path.stem
        out_dir = png_path.parent
        print(f"[INFO] Processing {png_path.name}...")

        # Save each measure as a separate file
        for s in ALL_SIZES:
            square = make_square(img, s)
            out_path = out_dir / f"{base}_{s}.ico"
            square.save(out_path, format="ICO", sizes=[(s, s)])
            print(f"  - {out_path.name}")

        # Save one multi-size file
        multi_path = out_dir / f"{base}.ico"
        img.save(multi_path, format="ICO", sizes=[(s, s) for s in ALL_SIZES])
        print(f"  - {multi_path.name} (multi-size)")
        print("[DONE]\n")

def main():
    if len(sys.argv) < 2:
        print("Usage: python png2ico.py <file.png>")
        return

    png_path = Path(sys.argv[1])
    if not png_path.exists():
        print(f"[ERR] File {png_path} not found.")
        return

    if png_path.suffix.lower() != ".png":
        print("[ERR] Only PNG files are supported.")
        return

    png_to_icos(png_path)

if __name__ == "__main__":
    main()