Change image transparency, but preserve color data

change_transparency.py

import argparse
import pathlib
from PIL import Image



def transparency_type(value, min=0, max=255):
	try:
		value = int(value)
		if min <= value <= max:
			return value
		else:
			raise argparse.ArgumentTypeError('value not in range %s-%s' % (min, max))
	except ValueError:
		raise argparse.ArgumentTypeError("invalid int value: '%s'" % (value))



description = (	"Change image transparency, but preserve color data. Examples:\n"
				"\tpython change_transparency.py -i in.png -t 0 -o out.png\n"
				"\tpython change_transparency.py -i out.png -t 255 -o restored.png\n")
parser = argparse.ArgumentParser(description=description, formatter_class=argparse.RawTextHelpFormatter, add_help=False)
required_args = parser.add_argument_group('Required arguments')
optional_args = parser.add_argument_group('Optional arguments')
optional_args.add_argument('--help', '-h', action='help', default=argparse.SUPPRESS, help='show this help message and exit')
required_args.add_argument('--input', '-i', type=pathlib.Path, help='path to input image', required=True)
required_args.add_argument('--transparency', '-t', type=transparency_type, metavar='0-255', help='target transparency (0-255)', required=True)
optional_args.add_argument('--output', '-o', type=pathlib.Path, help='path to output image')
args = parser.parse_args()



img = Image.open(args.input)
img = img.convert("RGBA")
items = img.getdata()

new_items = []
for item in items:
	new_items.append((item[0], item[1], item[2], args.transparency))

img.putdata(new_items)
img.save(args.output or args.input, "PNG")
print("Successful")

requirements.txt

Pillow==9.2.0
pathlib==1.0.1
argparse==1.4.0