Showing dynamically generated bitmap in ASP.NET page

Create a http handler that writes the bitmap to the response stream.

Heres a link on handlers themselves http://www.dotnetperls.com/ashx.

If you can write a file to the file system, using some form of naming convention, so that your not generating it over and over again.

If you have it written to a file you can write that to the response stream using context.Response.WriteFile(path);

You'll need to set appropriate headers for the response if you want to cahce something like the below should be ok.

        context.Response.Cache.SetCacheability(HttpCacheability.Public);
        context.Response.Cache.SetLastModified(lastWrite);
        context.Response.Cache.SetETag(string.Format("\"{0}\"", lastWrite.Ticks));
        context.Response.ContentType = "image/png";

you can check these headers on an incoming request and return a 304 with something like (do a null check before)

if (context.Request.Headers[since] >= lastwrite || context.Request.Headers[eTag] >= lastwriteTicks) {
            context.Response.StatusCode = 304;
            context.Response.StatusDescription = "Not Modified";
            return;
        }

If you need to generate fresh every time dont worry about caching and just write your iamge to the context.Response.OutputStream.