rgb.py

from collections import namedtuple
from operator import itemgetter, sub


class rgb:
    # https://www.w3.org/TR/REC-html40/types.html#h-6.5
    _NAMED_COLORS = {
        'black': 0x000000,
        'green': 0x008000,
        'silver': 0xC0C0C0,
        'lime': 0x00FF00,
        'gray': 0x808080,
        'olive': 0x808000,
        'white': 0xFFFFFF,
        'yellow': 0xFFFF00,
        'maroon': 0x800000,
        'navy': 0x000080,
        'red': 0xFF0000,
        'blue': 0x0000FF,
        'purple': 0x800080,
        'teal': 0x008080,
        'fuchsia': 0xFF00FF,
        'aqua': 0x00FFFF,
    }

    def __init__(self, a, b=None, c=None):
        if b is None and c is None:
            self.__value = a
        elif b is not None and c is not None:
            self.__value = (a << 16) | (b << 8) | c
        else:
            raise ValueError()

    def __getitem__(self, i):
        return (self.__value >> (2 - i)*8) & 0xff

    def __iter__(self):
        return (self[i] for i in range(3))

    def __repr__(self):
        return 'rgb({}, {}, {})'.format(*self)

    r, g, b = map(property, map(itemgetter, range(3)))
    
    def sq_dist(self, other):
        return sum(x*x for x in (a-b for a, b in zip(self, other)))

    def dist(self, other):
        return self.sq_dist(other) ** 0.5

    @classmethod
    def from_hexstring(cls, colorstr):
        hexstr = colorstr[1:]
        return cls(int(hexstr, 16))

    @classmethod
    def from_string(cls, colorstr):
        """
        1. #RRGGBB (TODO: #RGB)
        2. rgb(r, g, b)
        3. color name
        """
        if colorstr.startswith('#'):
            return cls.from_hexstring(colorstr)
        elif colorstr.startswith('rgb'):
            return eval(colorstr)
        elif colorstr in cls._NAMED_COLORS:
            return cls(cls._NAMED_COLORS[colorstr])
        else:
            raise ValueError('Invalid color: ' + colorstr)