import math


def perceived_brightness(rgb_color):
    """Compute perceived brightness.

    cf http://www.nbdtech.com/Blog/archive/2008/04/27/Calculating-the-Perceived-Brightness-of-a-Color.aspx
    Args:
        rgb_color (str): example 'rgb(215,200,80)'
    """
    rgb_color = rgb_color[4:-1]
    r, g, b = [int(i) for i in rgb_color.split(',')]
    return math.sqrt(r**2 * 0.241 + g**2 * 0.691 + b**2 * 0.068)