code: public static ImageWriter getWriterForFormat(String format) throws SlickException
  	{
  		ImageWriter writer = (ImageWriter) writers.get(format);
  		if (writer != null) {
  			return writer;
  		}
  		
  		writer = (ImageWriter) writers.get(format.toLowerCase());
  		if (writer != null) {
  			return writer;
  		}
  		
  		writer = (ImageWriter) writers.get(format.toUpperCase());
  		if (writer != null) {
  			return writer;
  		}
  		
  		throw new SlickException("No image writer available for: "+format);
  	}
docs: Get a Slick image writer for the given format
  
  @param format The format of the image to write
  @return The image write to use to produce these images
  @throws SlickException