function computeLuminance()
    {
        if (lighter)
            return (luminance + 0.05) * contrast - 0.05;
        else
            return (luminance + 0.05) / contrast - 0.05;
    }
Compute a desired luminance given a given luminance and a desired contrast
ratio.
@param {number} luminance The given luminance.
@param {number} contrast The desired contrast ratio.
@param {boolean} lighter Whether the desired luminance is lighter or darker
than the given luminance. If no luminance can be found which meets this
requirement, a luminance which meets the inverse requirement will be
returned.
@return {number} The desired luminance.