private static float commonOverPrintAlpha(float alpha) {
        // if alpha is already present we reduce it and we minimize
        // it if it is already lower then our over paint.  This an approximation
        // only for improved screen representation.
        if (alpha != 1.0f && alpha > OVERPAINT_ALPHA) {
            alpha -= OVERPAINT_ALPHA;
        } else if (alpha < OVERPAINT_ALPHA) {
//            alpha = 0.1f;
        } else {
            alpha = OVERPAINT_ALPHA;
        }
        return alpha;
    }