utils.py

import math

def hex_to_rgb(h):
    """
    Convert hex color values to RGB
    :param h: #RRGGBB
    :return: (r, g, b)
    """
    if isinstance(h, str):
        return tuple(int(h.lstrip('#')[i:i+2], 16) for i in (0, 2, 4))
    return h

def hex_to_rgb_norm(h):
    """
    convert hex color values to RGB, but normalizes it to fit in the range [0, 1]
    :param h: #RRGGBB
    :return: (r, g, b)
    """
    if isinstance(h, str):
        return tuple(int(h.lstrip('#')[i:i+2], 16) / 255 for i in (0, 2, 4))
    return h

def convert_K_to_RGB(colour_temperature):
    """
    Converts from K to RGB, algorithm courtesy of
    http://www.tannerhelland.com/4435/convert-temperature-rgb-algorithm-code/
    """
    # range check
    if colour_temperature < 1000:
        colour_temperature = 1000
    elif colour_temperature > 40000:
        colour_temperature = 40000

    tmp_internal = colour_temperature / 100.0

    # red
    if tmp_internal <= 66:
        red = 255
    else:
        tmp_red = 329.698727446 * math.pow(tmp_internal - 60, -0.1332047592)
        if tmp_red < 0:
            red = 0
        elif tmp_red > 255:
            red = 255
        else:
            red = tmp_red

    # green
    if tmp_internal <= 66:
        tmp_green = 99.4708025861 * math.log(tmp_internal) - 161.1195681661
        if tmp_green < 0:
            green = 0
        elif tmp_green > 255:
            green = 255
        else:
            green = tmp_green
    else:
        tmp_green = 288.1221695283 * math.pow(tmp_internal - 60, -0.0755148492)
        if tmp_green < 0:
            green = 0
        elif tmp_green > 255:
            green = 255
        else:
            green = tmp_green

    # blue
    if tmp_internal >= 66:
        blue = 255
    elif tmp_internal <= 19:
        blue = 0
    else:
        tmp_blue = 138.5177312231 * math.log(tmp_internal - 10) - 305.0447927307
        if tmp_blue < 0:
            blue = 0
        elif tmp_blue > 255:
            blue = 255
        else:
            blue = tmp_blue

    return tuple(map(lambda div: div/255.0, (red, green, blue)))