thumbnailWidth, thumbnailHeight, null);
                ImageIO.write(thumbnail, fessConfig.getThumbnailHtmlImageFormat(), outputFile);
                image.flush();
                return Result.OK;
            } finally {
                reader.dispose();
            }
        }
        return Result.FAILED;

     * The value is, e.g. png <br>
     * comment: Format of generated thumbnail images.
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getThumbnailHtmlImageFormat();

    /**
     * Get the value for the key 'thumbnail.html.image.xpath'. <br>
     * The value is, e.g. //IMG <br>
     * comment: XPath to select images for thumbnails.