code: public DiagramLayout getProcessDiagramLayout(InputStream bpmnXmlStream, InputStream imageStream) {
      Document bpmnModel = parseXml(bpmnXmlStream);
      return getBpmnProcessDiagramLayout(bpmnModel, imageStream);
    }
docs: Provides positions and dimensions of elements in a process diagram as
  provided by {@link RepositoryService#getProcessDiagram(String)}.
  
  Currently, it only supports BPMN 2.0 models.
  
  @param bpmnXmlStream
  BPMN 2.0 XML file
  @param imageStream
  BPMN 2.0 diagram in PNG format (JPEG and other formats supported
  by {@link ImageIO} may also work)
  @return Layout of the process diagram
  @return null when parameter imageStream is null