public InputStream getActivitiPicByProcessDefKey(String processDefKey){
        ProcessDefinitionEntity processDefinitionEntity = (ProcessDefinitionEntity) repositoryService.createProcessDefinitionQuery().processDefinitionKey(processDefKey).latestVersion().singleResult();
        //bpmnModel文件
        if(repositoryService instanceof  RepositoryServiceImpl){
            RepositoryServiceImpl repositoryService = (RepositoryServiceImpl)processEngine.getRepositoryService();
            BpmnModel bpmnModel2 = repositoryService.getBpmnModel(processDefinitionEntity.getId());
        }
        BpmnModel bpmnModel =   repositoryService.getBpmnModel(processDefinitionEntity.getId());
        List  activeActivityIds = new ArrayList<>(0);
        List highLightedFlows=new ArrayList<>(0);
        InputStream in = new DefaultProcessDiagramGenerator().generateDiagram(bpmnModel, "png", activeActivityIds,
                highLightedFlows,"宋体","宋体","宋体",null, 1.0);
        return in;
    }