Review

class PdfWriter {
    /**
     * Use this method to sets the default colorspace that will be applied
     * to all the document. The colorspace is only applied if another colorspace
     * with the same name is not present in the content.
     * <p>
     * The colorspace is applied immediately when creating templates and
     * at the page end for the main document content.
     * @param key the name of the colorspace. It can be <CODE>PdfName.DEFAULTGRAY</CODE>, <CODE>PdfName.DEFAULTRGB</CODE>
     * or <CODE>PdfName.DEFAULTCMYK</CODE>
     * @param cs the colorspace. A <CODE>null</CODE> or <CODE>PdfNull</CODE> removes any colorspace with the same name
     */
    public void setDefaultColorspace(final PdfName key, final PdfObject cs) {
        if (cs == null || cs.isNull())
            defaultColorspace.remove(key);
        defaultColorspace.put(key, cs);
    }

}