Transparent Windows user avatar

avatargen.py

import argparse
import subprocess
import pathlib
import winreg

#
# This script turned out to be quite large, so might as well document the recipe here..
# 
# Windows (like many services...) does not support transparent backgrounds for profile
#  pictures natively, it squashes beautiful, lossless, transparent .png files into
#  various .jpg files with some horrible rescaling algorithm.
#
# Luckily it can be coerced into showing .png files all around the OS, and even gets
#  transparency right!
#
# (As long as you are using a local user account, this won't work with Microsoft accounts.)
#
# To do so, you want to change some registry keys:
#
# HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\AccountPicture\Users\<SID>
#   Image32=...
#   Image40=...
#   Image64=...
#
# This however cannot be done by mere mortals, not even administrators. You have to use the
#  hidden SYSTEM user. For which it is best to use PsExec from SysInternals
#
# So the full recipe is:
#  Generate PNG files from your SVG with this very script
#  > $ whoami
#  > dave-pc\dave
#
#  > wmic useraccount where name = 'dave'
#  > SID
#  > ...
#
#  > psexec -i -d -s c:\windows\regedit.exe
#
# PS.: I am aware this is not particularly nice/very Pythonic code - it does what I need, nothing more
#

parser = argparse.ArgumentParser(
    prog = "avatargen",
    description = "Generate various resolution images for using as a profile picture from a vector image",
    epilog = ".. yes the hundredth iteration turned out great, but can we do better?"
)
parser.add_argument('filename')

# Configuration
file = pathlib.Path(parser.parse_args().filename)
targets = [
    # Windows
    {
        "name": "{}",
        "area": "bounds_circle",
        "sizes": [32, 40, 48, 64, 96, 192, 208, 240, 424, 448, 1080],
    },

    # Special sizes for "special" sites
    {
        "name": "github{}",
        "area": "bounds_circle",
        "sizes": [460]
    },
    {
        "name": "google{}",
        "area": "bounds_circle",
        "sizes": [500]
    },

    # Generic
    {
        "name": "square{}",
        "area": "bounds_square",
        "sizes": [512]
    },
    {
        "name": "circle{}",
        "area": "bounds_circle",
        "sizes": [512]
    }
]

print("Scanning for required software")

def enum_reg_keys(node):
    for index in range(1024):
        try:
            yield winreg.EnumKey(node, index)
        except EnvironmentError:
            break

inkscape = None
magick = None

roots = [
    r'Software\Microsoft\Windows\CurrentVersion\Uninstall',
    r'Software\WOW6432Node\Microsoft\Windows\CurrentVersion\Uninstall'
]
for root in roots:
    root = winreg.OpenKey(winreg.HKEY_LOCAL_MACHINE, root)

    for app in enum_reg_keys(root):
        app = winreg.OpenKey(root, app)
        icon = None
        
        try:
            icon = winreg.QueryValueEx(app, 'DisplayIcon')[0]
        except EnvironmentError:
            continue

        icon = pathlib.Path(icon)

        if icon.stem == "inkscape" and icon.suffix == ".exe":
            inkscape = icon.with_suffix('.com')

        if icon.stem == "ImageMagick":
            magick = icon.with_name('magick.exe')
        
print(f"Found Inkscape: {inkscape}")
print(f"Found ImageMagick: {magick}")

bounds = {}

print("Enumerating SVG elements looking for boundary elements")
output = subprocess.check_output([inkscape, '--query-all', file], shell=True)

for line in output.decode('utf-8').splitlines():
    line = line.split(',', 5)

    if line[0].startswith("bounds_"):
        x = float(line[1])
        y = float(line[2])
        w = float(line[3])
        h = float(line[4])

        bounds[line[0]] = [int(x), int(y), int(x+w), int(y+h)]

print("Rendering to intermediary supersized bitmaps")

actions = [
    f"file-open:{file}",
    f"export-type:png",
]

for i, target in enumerate(targets):
    for size in target.get('sizes'):
        name = target.get('name').format(size)
        
        area = bounds.get(target.get('area'))
        area = ':'.join([str(v) for v in area])
        
        res = size * 2

        actions += [
            f"export-filename: out/{name}",
            f"export-width: {res}",
            f"export-height: {res}",

            f"export-id: beaver",
            f"export-id-only",

            f"export-area: {area}",
            f"export-do"
        ]

actions = "; ".join(actions)
subprocess.check_call([inkscape, f'--actions={actions}'], shell=True)

print("Downsampling to final resolutions")

print(targets)

for target in targets:
    for size in target.get('sizes'):
        name = target.get('name').format(size)

        subprocess.check_call([
            magick,
            f'out/{name}.png', '-resize', '50%',
            f'out/{name}.png'
        ], shell=True)

print("Finished")