color.py

#coding: utf-8
# these code are from [ColorMeta](https://github.com/bcho/colormeta)

from PIL import Image


def rgb2xyz(r, g, b):
    # RGB to CIE XYZ REC 709
    # http://www.easyrgb.com/index.php?X=MATH&H=02#text2
    def _rgb(c):
        percentage = c / 255.0
        if percentage > 0.04045:
            return ((percentage + 0.055) / 1.055) ** 2.4 * 100
        else:
            return percentage / 12.92 * 100

    R = _rgb(r)
    G = _rgb(g)
    B = _rgb(b)

    x = R * 0.4124 + G * 0.3576 + B * 0.1805
    y = R * 0.2126 + G * 0.7152 + B * 0.0722
    z = R * 0.0193 + G * 0.1192 + B * 0.9505

    return (x, y, z)


def xyz2lab(x, y, z):
    # CIE XYZ REC 709 to CIE L*ab
    # http://www.easyrgb.com/index.php?X=MATH&H=07#text7
    ref = (96.4221, 100.000, 82.5221)

    def _xyz(c, ref_c):
        percentage = c / ref_c
        if percentage > 216 / 24389.0:
            return percentage ** (1 / 3.0)
        else:
            return ((24389 / 27.0) * percentage + 16) / 116.0

    X = _xyz(x, ref[0])
    Y = _xyz(y, ref[1])
    Z = _xyz(z, ref[2])

    L = (116 * Y) - 16
    a = 500 * (X - Y)
    b = 200 * (Y - Z)

    return (L, a, b)


def rgb2lab(r, g, b):
    x, y, z = rgb2xyz(r, g, b)
    return xyz2lab(x, y, z)


def deltaE(a, b):
    # Delta E CIE76
    # http://en.wikipedia.org/wiki/Color_difference#Delta_E
    # JND = 2.3
    delta_e = 0
    for pair in zip(a, b):
        delta_e += (pair[0] - pair[1]) ** 2

    return delta_e ** 0.5


def _open_image(filename):
    return Image.open(filename)


def _save_image(image, filename):
    image.save(filename)
    return


def _color_quantization(image, color_count):
    try:
        return image.convert('P', palette=Image.ADAPTIVE,
                colors=color_count)
    except:
        image = image.convert('RGB')
        return image.convert('P', palette=Image.ADAPTIVE,
                colors=color_count)


def _to_hex(num):
    return "#%02x%02x%02x" % num


def _get_palette(image, color):
    l = image.getpalette()[0:color * 3]
    return [tuple(l[i:i + 3]) for i in range(0, len(l), 3)]


def _get_hex_palette(image, color):
    return [_to_hex(i) for i in _get_palette(image, color)]


def _get_colors(image, color_count, diff, count):
    def __compare(sample, control_group):
        def is_notice(a, b):
            lab_a = rgb2lab(a[0], a[1], a[2])
            lab_b = rgb2lab(b[0], b[1], b[2])
            return deltaE(lab_a, lab_b) < diff

        for color in control_group:
            if is_notice(sample, color):
                return False
        return True

    def __pop(l):
        while l:
            yield [l.pop(0) for i in xrange(3)]

    payload = image.getpalette()[0:count * 3]
    ret = []
    for i in __pop(payload):
        if not __compare(i, ret):
            continue
        else:
            ret.append(tuple(i))
        if len(ret) == color_count:
            break

    return ret

image = _open_image('colorful.png')