报表服务器决策报表访问背景图片会变成空白的，后台日志报错

java.lang.Exception: Not image file!

at com.fr.web.AttachmentHelper.getImgType(Unknown Source)

at com.fr.web.AttachmentHelper.outputAttachment(Unknown Source)

at com.fr.web.AttachmentHelper.output(Unknown Source)

at com.fr.web.core.A.F.actionCMD(Unknown Source)

at com.fr.web.core.ActionNoSessionCMD.actionCMD(Unknown Source)

at com.fr.web.core.WebActionsDispatcher.dealForActionCMD(Unknown Source)

at com.fr.web.core.WebActionsDispatcher.dealForActionDefaultCmd(Unknown Source)

at com.fr.web.core.A.C.process(Unknown Source)

at com.fr.web.core.ReportDispatcher.dealWithOp(Unknown Source)

at com.fr.web.core.ReportDispatcher.dealWeblet(Unknown Source)

at com.fr.web.core.ReportDispatcher.dealWithRequest(Unknown Source)

at com.fr.web.controller.BaseRequestService.preview(Unknown Source)

at com.fr.web.controller.FormRequestService.preview(Unknown Source)

at sun.reflect.GeneratedMethodAccessor191.invoke(Unknown Source)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:498)

at com.fr.third.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)

at com.fr.third.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)

at com.fr.third.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)

at com.fr.third.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:747)

at com.fr.third.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:676)

at com.fr.third.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)

at com.fr.third.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:938)

at com.fr.third.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870)

at com.fr.third.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)

at com.fr.third.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)

at com.fr.third.springframework.web.servlet.FrameworkSe