color variant fix

color.py

# Fix for http://chase-seibert.github.io/blog/2011/07/29/python-calculate-lighterdarker-rgb-colors.html

def color_variant(hex_color, brightness_offset=1):
    """ takes a color like #87c95f and produces a lighter or darker variant """
    if len(hex_color) != 7:
        raise Exception("Passed %s into color_variant(), needs to be in #87c95f format." % hex_color)
    rgb_hex = [hex_color[x:x+2] for x in [1, 3, 5]]
    new_rgb_int = [int(hex_value, 16) + brightness_offset for hex_value in rgb_hex]
    new_rgb_int = [min([255, max([0, i])]) for i in new_rgb_int] # make sure new values are between 0 and 255
    # hex() produces "0x88", we want just "88"
    return "#" + "".join([hex(i)[2:] if len(hex(i)[2:]) == 2 else '0' + hex(i)[2:] for i in new_rgb_int])

    # OLD:
    # return "#" + "".join([hex(i)[2:] for i in new_rgb_int])
"""
OLD: color_variant('#ff8022', -20) == '#eb6ce'
NEW: color_variant('#ff8022', -20) == '#eb6c0e'
"""