ChartDirector求助：用了jsp过滤器后不出图

[zhoufei004]

1、jsp代码
String chart1URL = c.makeSession(request, "chart1");
<img src='<%=response.encodeURL("getchart.jsp?"+chart1URL)%>' usemap="#map1" border="0">

2、过滤器
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

HttpServletRequest req=(HttpServletRequest)request;
HttpServletResponse resp=(HttpServletResponse)response;
HttpSession session=req.getSession(true);
resp.setContentType("text/html");
resp.setCharacterEncoding("UTF-8");
PrintWriter out=resp.getWriter();
String request_uri=req.getRequestURI();
String ctxPath=req.getContextPath();
String uri=request_uri.substring(ctxPath.length());

if(uri.contains("Login.jsp")||uri.contains("Login")||uri.contains("getchart")||uri.contains(".png")||uri.contains(".jpg")||uri.contains(".css")||uri.contains(".js")||uri.contains("testchart.jsp")) {
chain.doFilter(request, response);
}else {
if(null !=session.getAttribute("user")) {
chain.doFilter(request, response);
}else {
out.println("您还没有登录，请先登录！3秒后回到登录页面。");
resp.setHeader("refresh","3;url="+ctxPath+"/Login.jsp");
return;
}
}

}

3、问题
无过滤器显示正常，上报过滤器，图片不显示。

【求解，期待大神回复！！！】