Convert Kelvin Temperatures to RGB values with given colorspace primaries.

blackbody_to_rgb.py

"""
Convert Kelvin Temperatures to RGB values with given colorspace primaries.

Author: Liam Collod
Last Modified: 02/02/2021

Require colour-science >= 0.3.16
"""

import colour
import numpy


def blackbody_to_RGB(temperature, colorspace, illuminants=None, cctf_encoding=False, clip=True):
    """

    Args:
        clip(bool): If True value should be clipped between the 0-1 range
        illuminants: if specified this iiluminant will be used instead of hte colorspace whitepoint. ex: 'E'
        temperature(int): temperature in Kelvin to compute
        colorspace(str): colorspace model, ex: 'sRGB' or 'ACEScg'
        cctf_encoding(bool): apply the cttf encoding ?

    Returns:
        numpy.ndarray: 1D array

    """
    csm = colour.RGB_COLOURSPACES[colorspace]
    if illuminants:
        illuminant_lab = colour.CCS_ILLUMINANTS['CIE 1931 2 Degree Standard Observer'][illuminants]
    else:
        illuminant_lab = csm.whitepoint

    XYZ = colour.sd_to_XYZ(colour.sd_blackbody(temperature), k=683)
    RGB = colour.XYZ_to_RGB(XYZ, illuminant_lab, csm.whitepoint, csm.matrix_XYZ_to_RGB)
    if cctf_encoding:
        colour.cctf_encoding(RGB, colorspace)

    if clip:
        RGB = colour.utilities.normalise_maximum(RGB, clip=clip)

    return RGB


def display_temp2rgb_range(min_temp, max_temp, increment, colorspace, clip):
    """ Print the RGB values for the temparature in the given range.

    Args:
        min_temp(int): Kelvin temparature: beginning of range
        max_temp(int): Kelvin temparature: end of range
        increment(int): step of range
        colorspace(str): colorspace model, ex: 'sRGB' or 'ACEScg'

    Returns:
        None
    """
    print(f"RGB values with {user_colorspace} primaries for temperature in range [{min_temp}, {max_temp}] : \n")
    for temp in range(min_temp, max_temp, increment):
        rgb_result = blackbody_to_RGB(temp, colorspace=colorspace, cctf_encoding=False, clip=clip)
        print(f"{temp}K: {rgb_result}")

    return


if __name__ == '__main__':

    user_temperature = 1500
    user_colorspace = 'ACEScg'

    """ Bottom code is to display the above temperature to an RGB value with the given primaries above."""
    # result = blackbody_to_RGB(1500, 'sRGB', cctf_encoding=False, clip=True)
    # print(f"RGB values with {user_colorspace} primaries for temperature {user_temperature} : \n"
    #       f"  > {result}")

    """ Bottom code is to display multiples temperature to RGB at the same time (just uncomment)"""
    display_temp2rgb_range(min_temp=1000, max_temp=11500, increment=250, colorspace=user_colorspace, clip=True)