code: public boolean write(File targetFile) throws IORuntimeException {
  		final String formatName = FileUtil.extName(targetFile);
  		if (StrUtil.isNotBlank(formatName)) {
  			this.targetImageType = formatName;
  		}
  		
  		if(targetFile.exists()) {
  			targetFile.delete();
  		}
  		
  		ImageOutputStream out = null;
  		try {
  			out = ImgUtil.getImageOutputStream(targetFile);
  			return write(out);
  		} finally {
  			IoUtil.close(out);
  		}
  	}
docs: 写出图像为目标文件扩展名对应的格式
  
  @param targetFile 目标文件
  @return 是否成功写出，如果返回false表示未找到合适的Writer
  @throws IORuntimeException IO异常