code: public static Map<String, PictureData> getPicMap(Workbook workbook, int sheetIndex) {
  		Assert.notNull(workbook, "Workbook must be not null !");
  		if (sheetIndex < 0) {
  			sheetIndex = 0;
  		}
  
  		if (workbook instanceof HSSFWorkbook) {
  			return getPicMapXls((HSSFWorkbook) workbook, sheetIndex);
  		} else if (workbook instanceof XSSFWorkbook) {
  			return getPicMapXlsx((XSSFWorkbook) workbook, sheetIndex);
  		} else {
  			throw new IllegalArgumentException(StrUtil.format("Workbook type [{}] is not supported!", workbook.getClass()));
  		}
  	}
docs: 获取工作簿指定sheet中图片列表
  
  @param workbook 工作簿{@link Workbook}
  @param sheetIndex sheet的索引
  @return 图片映射，键格式：行_列，值：{@link PictureData}