flowable 6.4.1 流程图展示（动态流程图）乱码问题

运用flowable处理工作流时，难免会用到一个功能，就是查看流程图当前进展或者说走向，但是流程图输出到页面一直是乱码，有的大神说是字体问题，设置成宋体就好了：

import org.flowable.spring.SpringProcessEngineConfiguration;
import org.flowable.spring.boot.EngineConfigurationConfigurer;
import org.springframework.context.annotation.Configuration;

@Configuration
public class FlowableConfig implements EngineConfigurationConfigurer<SpringProcessEngineConfiguration> {


    @Override
    public void configure(SpringProcessEngineConfiguration engineConfiguration) {
        engineConfiguration.setActivityFontName("宋体");
        engineConfiguration.setLabelFontName("宋体");
        engineConfiguration.setAnnotationFontName("宋体");
    }
}

但是我的还是不行，尝试了很多方法，最后靠一个工具类操作输入输出流解决了

javax.imageio.ImageIO;

贴上代码，有遇到类似问题的可以参考：

/**
     * 查看当前流程图已到达节点
     * @param httpServletResponse
     * @param processId 流程实例id
     * @throws IOException
     */
    @ApiOperation("查看流程图")
    @GetMapping("/genProcessDiagrams")
    public void genProcessDiagrams(HttpServletResponse httpServletResponse, String processId) throws IOException{
        ProcessInstance pi = runtimeService.createProcessInstanceQuery().processInstanceId(processId).singleResult();
        //流程走完的不显示图
        if (pi == null) {
            return;
        }

        //获得活动的节点
        List<HistoricActivityInstance> historyProcess =  historyService.createHistoricActivityInstanceQuery().processInstanceId(processId).orderByHistoricActivityInstanceStartTime().asc().list();

        List<String> activityIds = new ArrayList<>();
        List<String> flows = new ArrayList<>();
        //获取流程图
        BpmnModel bpmnModel = repositoryService.getBpmnModel(pi.getProcessDefinitionId());
        for (HistoricActivityInstance hi : historyProcess) {
            String activityType = hi.getActivityType();
            if (activityType.equals("sequenceFlow") || activityType.equals("exclusiveGateway")) {
                flows.add(hi.getActivityId());
            } else if (activityType.equals("userTask") || activityType.equals("startEvent")) {
                activityIds.add(hi.getActivityId());
            }
        }
        List<Task> tasks = taskService.createTaskQuery().processInstanceId(processId).list();
        for (Task task : tasks) {
            activityIds.add(task.getTaskDefinitionKey());
        }
        ProcessEngineConfiguration engConf = processEngineConfiguration;
        //定义流程画布生成器
        ProcessDiagramGenerator processDiagramGenerator = engConf.getProcessDiagramGenerator();
        InputStream in = processDiagramGenerator.generateDiagram(bpmnModel, "png", activityIds, flows, engConf.getActivityFontName()
                , engConf.getLabelFontName(), engConf.getAnnotationFontName(), engConf.getClassLoader(), 1.0, true);

        // 设置响应的类型格式为图片格式
        httpServletResponse.setContentType("image/png");
        //禁止图像缓存。
        httpServletResponse.setHeader("Pragma", "no-cache");
        httpServletResponse.setHeader("Cache-Control", "no-cache");
        httpServletResponse.setDateHeader("Expires", 0);

        OutputStream out = null;
        byte[] buf = new byte[1024];
        int legth = 0;
        try {

            out = httpServletResponse.getOutputStream();
            BufferedImage buffImg = null;
            buffImg = ImageIO.read(in);
            ImageIO.write(buffImg, "png", out);

        }catch (IOException e){
            e.printStackTrace();
        } finally {
            if (in != null) {
                in.close();
            }
            if (out != null) {
                out.close();
            }
        }
    }