Convert colon separated hex color strings into palette images and vice versa

palette-image

#!/usr/bin/python
import sys
from PIL import Image, ImageDraw, ImageColor
from argparse import ArgumentParser

cell_w = cell_h = 40

def color_to_hex(color):
    return '#' + ''.join('%02x' % x for x in color)

def to_image(input_file, output_file, delim):
    if input_file == '-':
        input_file = sys.stdin
    else:
        input_file = open(input_file, 'r')

    if output_file == '-':
        output_file = open(sys.stdout, 'wb')
    else:
        output_file = open(output_file, 'wb')

    hex_codes = input_file.read().strip().split(delim)

    img = Image.new('RGB', (cell_w * len(hex_codes), cell_h))
    draw = ImageDraw.Draw(img)

    for i, color_code in enumerate(hex_codes):
        color = ImageColor.getrgb(color_code) 
        draw.rectangle(((cell_w * i, 0),
                        (cell_w * (i + 1), cell_h)), 
                       color)

    img.save(output_file, "PNG")

def from_image(input_file, output_file, delim):
    if input_file == '-':
        input_file = sys.stdin.dettach()
    else:
        input_file = open(input_file, 'rb')

    if output_file == '-':
        output_file = open(sys.stdout, 'w')
    else:
        output_file = open(output_file, 'w')

    img = Image.open(input_file)
    num_colors = img.size[0] // cell_w

    hex_codes = []
    for i in range(num_colors):
        color = img.getpixel((i * cell_w, 0))
        hex_codes.append(color_to_hex(color))

    output_file.write(delim.join(hex_codes) + '\n')
    output_file.close()


if __name__ == "__main__":
    parser = ArgumentParser(description=
            "Converts a list of hex colors into an image and vice versa.")

    group_action = parser.add_mutually_exclusive_group(required=True)
    group_action.add_argument("--to-image", dest="to_image", action="store_true")
    group_action.add_argument("--from-image", dest="from_image", action="store_true")
    parser.add_argument("-d", dest="delimiter", default=":", type=str)
    parser.add_argument("input_file", type=str)
    parser.add_argument("output_file", type=str)

    args = parser.parse_args()

    if args.to_image:
        to_image(args.input_file, args.output_file, args.delimiter)
    else:
        from_image(args.input_file, args.output_file, args.delimiter)