svg2ico.py

from PIL import Image  # https://packages.ubuntu.com/jammy/python3-pil  https://pypi.org/project/Pillow/
import cairosvg.surface  # https://packages.ubuntu.com/jammy/python3-cairosvg  https://pypi.org/project/CairoSVG/  

from io import BytesIO


def svg2ico(*args, resolutions={128, 96, 64, 48, 32, 16}, write_to=None, dpi=96, winxp_compat=False, **kwargs):
	maxres = max(resolutions, key=lambda res: (0, res) if res is not None else (1, ), default=None)
	# "DPI" from https://github.com/Kozea/CairoSVG/blob/2.2.0/cairosvg/__init__.py#L62
	imsave_kwargs = {'format': 'ICO'}
	if winxp_compat:
		# Needs at least Pillow 8.3.0 (released July 2021)
		# https://github.com/python-pillow/Pillow/issues/2512
		imsave_kwargs['bitmap_format'] = 'bmp'

	t = cairosvg.surface.Tree(*args, **kwargs)
	imsave_kwargs['append_images'] = []
	for res in resolutions:
		f = BytesIO()
		cairosvg.surface.PNGSurface(t, f, dpi,
		  output_width=res, output_height=res).finish()
		f.seek(0)
		if res is maxres:
			im_main = Image.open(f)
		else:
			imsave_kwargs['append_images'].append(Image.open(f))

	if write_to is None:
		f = BytesIO()
		im_main.save(f, **imsave_kwargs)
		return f.get_value()

	return im_main.save(write_to, **imsave_kwargs)

if __name__ == '__main__':
	import sys, os
	i, o = sys.argv[1:]
	svg2ico(url=i, write_to=(o or sys.stdout.buffer))