引言：项目需要预览OFD文件，但前端对OFD文件支持太差，因此将OFD文件直接转换成PNG格式、Base64编码的数据并返回给前端

依赖

 <dependency><groupId>org.ofdrw</groupId><artifactId>ofdrw-converter</artifactId><version>1.17.2</version><!--  如果项目已经引入了log4j，则排除log4j        --><exclusions><exclusion><groupId>org.apache.logging.log4j</groupId><artifactId>log4j-slf4j-impl</artifactId></exclusion></exclusions>
</dependency>

接口

/*** ofd文件转换成png图片* @return* @throws Exception*/@GetMapping(value = "/getOfdToPng")public Result<List<String>> getOfdToPng() throws Exception {long start = System.currentTimeMillis();// 这里是minio访问urlString ofdPath = "http://127.0.0.1:9000/ofd/42181c66_20240531_%E8%88%AA%E4%BD%B3%EF%BC%88%E6%8A%95%E6%A0%87%EF%BC%89%E5%AD%972024%E5%B9%B4%E7%AC%ACHJ000033%E5%8F%B7%E4%BF%9D%E5%87%BD.ofd?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=minioadmin%2F20240612%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20240612T080307Z&X-Amz-Expires=604800&X-Amz-SignedHeaders=host&versionId=null&X-Amz-Signature=30626032831f76333120327cba020c4aaffcf68c27912d629bf31c99d37b6aa9";InputStream isFromUrl = DocUtils.getIsFromUrl(ofdPath);List<String> list = new ArrayList<>();// 输入OFD文件路径// 输出图片路径try (OFDReader reader = new OFDReader(isFromUrl)) {// ppm 设置来指定图片生成的分辨率，数值越高图片越清晰,生成时间越慢ImageMaker imageMaker = new ImageMaker(reader,16);int pageSize = imageMaker.pageSize();for (int i = 0; i < pageSize; i++) {BufferedImage bufferedImage = imageMaker.makePage(i);ByteArrayOutputStream outputStream = new ByteArrayOutputStream();ImageIO.write(bufferedImage, "png", outputStream);byte[] imageBytes = outputStream.toByteArray();// 生成base64格式的图片String base64String = "data:image/png;base64," + Base64.getEncoder().encodeToString(imageBytes);outputStream.close();list.add(base64String);}} catch (IOException e) {e.printStackTrace();}finally {isFromUrl.close();}long end = System.currentTimeMillis();System.out.println("耗费时间：" + (end -start) * 1.0 / 1000);return Result.ok(list);}// 将远程url转换成InputStream public static InputStream getIsFromUrl(String remoteUrl) throws Exception {byte[] fileBytes = null;InputStream inStream = null;ByteArrayOutputStream bOutStream = null;try {URL url = new URL(remoteUrl);HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();httpConn.connect();inStream = httpConn.getInputStream();return inStream;} catch (UnknownHostException e) {String msg = MessageFormat.format("网络请求时发生UnknownHostException异常: {0}", e.getMessage());Exception ex = new Exception(msg);ex.initCause(e);throw ex;} catch (MalformedURLException e) {String msg = MessageFormat.format("网络请求时发生MalformedURLException异常: {0}", e.getMessage());Exception ex = new Exception(msg);ex.initCause(e);throw ex;} catch (IOException e) {String msg = MessageFormat.format("从远程Url中获取文件流时发生IOException异常: {0}", e.getMessage());Exception ex = new Exception(msg);ex.initCause(e);throw ex;}}

前端展示

请求接口

getAction("/getOfdToPng").then(res =>{this.imgList = res.result})

因为是PNG格式、Base64编码的数据，可以直接使用img标签

<div style="display:flex;justify-content:center;" v-for="img in imgList" :key="img"><img class="imgOfd" :src="img"></div>