Remap OSH Park PCB preview images to other soldermask and silkscreen colours

OSHPark_colour_mod.py

#!/usr/bin/env python3

import argparse
import struct
from PIL import Image

if __name__ == "__main__":
    colour_map = {
        (193, 177, 203) : (193, 177, 203),# silkscreen
        (197, 183, 208) : (197, 183, 208), # silkscreen + copper
        (88, 88, 87) : (88, 88, 87), # PCB substrate
        (0, 0, 0) : (0, 0, 0), # black background
        (51, 0, 85) : (51, 0, 85), # soldermask
        (177, 136, 131) : (177, 136, 131), # copper
        (64, 18, 100) : (64, 18, 100) # soldermask + copper
    }

    parser = argparse.ArgumentParser(description="Utility for remapping OSH Park preview image colours")
    parser.add_argument('-i', dest='input', metavar='<input>', 
                        required=True, type=str, help="Input file")
    parser.add_argument('-o', dest='output', metavar='<output>',
                        type=str, help="Output file")
    parser.add_argument('-m', dest='mask', metavar='<mask>',
                        type=str, help="Soldermask colour in hex format")
    parser.add_argument('-s', dest='silkscreen', metavar='<silkscreen>',
                        type=str, help="Silkscreen colour in hex format")
    args = parser.parse_args()

    if args.mask:
        r, g, b = struct.unpack('BBB',bytes.fromhex(args.mask))
        colour_map[(51, 0, 85)] = (r,g,b)
        rn = r + 13
        gn = g + 18
        bn = b + 15
        colour_map[(64, 18, 100)] = (rn,gn,bn)
    if args.silkscreen:
        r, g, b = struct.unpack('BBB',bytes.fromhex(args.silkscreen))
        colour_map[(193, 177, 203)] = (r,g,b)
        rn = r + 4
        gn = g + 6
        bn = b + 5
        colour_map[(197, 183, 208)] = (rn,gn,bn)

    im = Image.open(args.input)
    print(im.format, im.size, im.mode)
    out_img = Image.new('RGBA', im.size, (0,0,0,0))
    pixels = out_img.load()
    rgba_im = im.convert('RGBA')
    for x in range(im.size[0]):
        for y in range(im.size[1]):
            r, g, b, a = rgba_im.getpixel((x, y))
            if a != 0:
                rn, gn, bn = colour_map[(r,g,b)]
                pixels[x,y] = (rn, gn, bn, a)

    if args.output:
        out_img.save(args.output)
    else:
        out_img.show()