public static int modulateAlpha(int colorAlpha, int alpha) {
        int scale = alpha + (alpha >>> 7);  // convert to 0..256
        return colorAlpha * scale >>> 8;
    }
Modulate the colorAlpha to new alpha

@param colorAlpha Color's alpha
@param alpha      Modulate alpha
@return Modulate alpha
caprice/ui/src/main/java/net/qiujuer/genius/ui/Ui.java