* @param   green   the intensity of green. A value between 0 and 1
     * @param   blue    the intensity of blue. A value between 0 and 1
     */
    private void HelperRGB(float red, float green, float blue) {
    	PdfXConformanceImp.checkPDFXConformance(writer, PdfXConformanceImp.PDFXKEY_RGB, null);
        if (red < 0)
            red = 0.0f;
        else if (red > 1.0f)
            red = 1.0f;
        if (green < 0)
            green = 0.0f;
        else if (green > 1.0f)
            green = 1.0f;
        if (blue < 0)
            blue = 0.0f;
        else if (blue > 1.0f)
            blue = 1.0f;
        content.append(red).append(' ').append(green).append(' ').append(blue);
    }