flowable 根据xml 字符串生成流程图

          //获取xml
        InputStream stream = repositoryService.getProcessModel(processDefinitionId);

      
        String result = IOUtils.toString(stream, StandardCharsets.UTF_8);

        // 创建 XMLInputFactory
        XMLInputFactory factory = XMLInputFactory.newInstance();

        // 从字符串创建 XMLStreamReader
        XMLStreamReader reader = factory.createXMLStreamReader(new StringReader(result));

        BpmnModel bpmnModel = new BpmnXMLConverter().convertToBpmnModel(reader);

        final ProcessDiagramGenerator diagramGenerator =                
                                processEngineConfiguration.getProcessDiagramGenerator();

        // 使用Flowable的内置方法生成SVG图像
        InputStream svgImage = diagramGenerator.generateJpgDiagram(bpmnModel);

        ByteArrayOutputStream out = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int len;
        while ((len = svgImage.read(buffer, 0, 1024)) != -1) {
            out.write(buffer, 0, len);
        }

        byte[] pngBytes = out.toByteArray();

       String base64= Base64.getEncoder().encodeToString(pngBytes);