final BufferedImage image = reader.read(0, param);
                final int thumbnailWidth = fessConfig.getThumbnailHtmlImageThumbnailWidthAsInteger();
                final int thumbnailHeight = (int) ((height > width ? width : height)
                        * fessConfig.getThumbnailHtmlImageThumbnailWidthAsInteger().floatValue() / width);

     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     * @throws NumberFormatException When the property is not integer.
     */
    Integer getThumbnailHtmlImageThumbnailWidthAsInteger();

    /**
     * Get the value for the key 'thumbnail.html.image.thumbnail.height'. <br>
     * The value is, e.g. 100 <br>
     * comment: Height of generated thumbnail images.