Invert all colours in a CSS file.

colour-inverter.py

#!/usr/bin/env python

# Concept taken from http://code.activestate.com/recipes/527747-invert-css-hex-colors/
# Modified to take the css filename as an argument and also handle rgb() and rgba() values
#
# To run:
#     python ./colour-inverter.py <path/to/file.css>

import os
import re
import sys

if not (len(sys.argv) > 1 and os.path.isfile(sys.argv[1])):
    print('You must specify a css file to invert')
    sys.exit(1)

re_hex = re.compile("#([0-9a-f]{3,6})(\W)?", re.IGNORECASE)
re_rgb = re.compile("(rgba?)\( ?(\d{1,3}), ?(\d{1,3}), ?(\d{1,3}) ?(, [\d\.]{1,})?\)", re.IGNORECASE)

def invert_hex(content):
    text = content.group(1).lower()
    code = {}
    l1="0123456789abcdef"
    l2="fedcba9876543210"
    for i in range(len(l1)):
        code[l1[i]]=l2[i]
    inverted = ""
    for j in text:
        inverted += code[j]
    return '#{}{}'.format(inverted, content.group(2))

def invert_rgb(content):
    rgb = content.group(1)
    num1 = 255 - int(content.group(2))
    num2 = 255 - int(content.group(3))
    num3 = 255 - int(content.group(4))
    alpha = content.group(5)
    return '{}({}, {}, {}{})'.format(rgb, num1, num2, num3, alpha)

inputfile = sys.argv[1]
content = file(inputfile,'r').read()

print('Converting 6 digit hex...')
content = re_hex.sub(invert_hex, content)
print('Converting rgb...')
content = re_rgb.sub(invert_rgb, content)

outputfile = inputfile[:-4]+"-inverted.css"
out = file(outputfile,'w')
out.write(content)
out.close()

Great updates! Thanks @treatmesubj!