With the html as follows:

<img src="/myWebAppContext/myAction!default.action />

xwork.xml could be as follows:

<xwork>
    ...
    <result-types>
        <result-type name="myBytesResult" class="foo.bar.MyBytesResult" />
    </result-types>
    ...

    <action name="myAction" class="...">
        <result name="myImageResult" type="myBytesResult">
            <param name="contentType">${myContentType}</param>
            <param name="contentDisposition">${myContentDisposition}</param>
            <param name="contentLength">${myContentLength}</param>
            <param name="bufferSize">${myBufferSize}</param>
        <result>
    </action>

    ...
</xwork>

the action could be as follows:

public class MyAction extends ActionSupport {
   public String doDefault() {
        return "myImageResult";
    }
   public byte[] getMyImageInBytes() { .... }

   public String getMyContentType() { ... }
   public String getMyContentDisposition() { ... }
   public int getMyContentLength() { .... }
   public int getMyBufferSize() { ... }
}
public class MyBytesResult implements Result {

	public void execute(ActionInvocation invocation) throws Exception {
		MyAction action = (MyAction) invocation.getAction();
		HttpServletResponse response = ServletActionContext.getResponse();
		
                response.setContentType(action.getContentType());
		response.setContentLength(action.getContentLength());
		
		response.getOutputStream().write(action.getImageInBytes());
		response.getOutputStream().flush();
	}

}