PNG-to-ICNS.py

# Run this script using following command
# $ python generate-iconset.py icon.png  
# Then execute the following command to create .icns
# $ iconutil -c icns icon.iconset

import os
import sys
import pathlib
import subprocess

if len(sys.argv) < 2:
    print("No path to original / hi-res icon provided")
    raise SystemExit

if len(sys.argv) > 2:
    print("Too many arguments")
    raise SystemExit

originalPicture = sys.argv[1]
if not (os.path.isfile(originalPicture)):
    print(f"There is no such file: {sys.argv[1]}")
    raise SystemExit

fname = pathlib.Path(originalPicture).stem
ext = pathlib.Path(originalPicture).suffix
destDir = pathlib.Path(originalPicture).parent

iconsetDir = os.path.join(destDir, f"{fname}.iconset")
if not (os.path.exists(iconsetDir)):
    pathlib.Path(iconsetDir).mkdir(parents=False, exist_ok=True)

class IconParameters():
    width = 0
    scale = 1
    def __init__(self,width,scale):
        self.width = width
        self.scale = scale
    def getIconName(self):
        if self.scale != 1:
            return f"icon_{self.width}x{self.width}{ext}"
        else:
            return f"icon_{self.width//2}x{self.width//2}@2x{ext}"

# https://developer.apple.com/design/human-interface-guidelines/macos/icons-and-images/app-icon#app-icon-sizes
ListOfIconParameters = [
    IconParameters(16, 1),
    IconParameters(16, 2),
    IconParameters(32, 1),
    IconParameters(32, 2),
    IconParameters(64, 1),
    IconParameters(64, 2),
    IconParameters(128, 1),
    IconParameters(128, 2),
    IconParameters(256, 1),
    IconParameters(256, 2),
    IconParameters(512, 1),
    IconParameters(512, 2),
    IconParameters(1024, 1),
    IconParameters(1024, 2)
]

# generate iconset
for ip in ListOfIconParameters:
    subprocess.call(["sips", "-z", str(ip.width), str(ip.width), originalPicture, "--out", os.path.join(iconsetDir, ip.getIconName())])
    #print(f"Generated {ip.getIconName()}")

# convert iconset to icns file
subprocess.call(["iconutil", "-c", "icns", iconsetDir, "-o", os.path.join(destDir, f"{fname}.icns")])