Plugin for one-color https://github.com/One-com/one-color. Function calculates perceived brightness of a passed color.

perceived-brightness.js

function pB (algo) {

    var algorithm = algo || 'rec2020';
    var rgb = this.rgb();

    if (algorithm === 'rec2020') {

        // https://en.wikipedia.org/wiki/Rec._2020
        return ( (rgb._red * 2627) + (rgb._green * 6780) + (rgb._blue * 593) ) / 10000;

    } else if (algorithm === 'w3c') {

        // http://www.w3.org/TR/AERT#color-contrast
        return ( (rgb._red * 299) + (rgb._green * 587) + (rgb._blue * 114) ) / 1000;

    } else if (algorithm === 'nbd') {

        // http://www.nbdtech.com/Blog/archive/2008/04/27/Calculating-the-Perceived-Brightness-of-a-Color.aspx
        return Math.sqrt( (Math.pow(rgb._red, 2) * .241) + (Math.pow(rgb._green, 2) * .691) + (Math.pow(rgb._blue, 2) * .068) );

    } else if (algorithm === 'rec709') {

        // https://en.wikipedia.org/wiki/Relative_luminance ; https://en.wikipedia.org/wiki/Rec._709
        return ( (rgb._red * 241) + (rgb._green * 691) + (rgb._blue * 68) ) / 1000;

    } else {

        // default rec2020
        return ( (rgb._red * 2627) + (rgb._green * 6780) + (rgb._blue * 593) ) / 10000;

    }

}

one.color.installMethod('perceivedBrightness', pB);
//ONECOLOR.installMethod('perceivedBrightness', pB);