docs: public static ImageWriter getWriter(String formatName) {
  		ImageWriter writer = null;
  		Iterator<ImageWriter> iter = ImageIO.getImageWritersByFormatName(formatName);
  		if (iter.hasNext()) {
  			writer = iter.next();
  		}
  		if (null == writer) {
  			// 尝试扩展名获取
  			iter = ImageIO.getImageWritersBySuffix(formatName);
  			if (iter.hasNext()) {
  				writer = iter.next();
  			}
  		}
  		return writer;
  	}