This question is related this one: Cannot render image to HttpContext.Response.OutputStream. It is not a duplicate.
When attempting to save a PNG to the Response.OutputStream I am experiencing inconsistent behavior between the local development environment and the production environment. Namely, the code I was using originally worked fine locally, but failed on the production server.
Here is the original code which worked locally:
using (Bitmap bmp = challenge.RenderImage()) {
bmp.Save(context.Response.OutputStream, ImageFormat.Png);
}
Despite working locally, when I deployed that on the production server I received an Application Error:
A generic error occurred in GDI+.
After some digging I determined that the problem was in the fact that 'Saving a PNG image requires a seekable stream.'- which the Response.OutputStream is not. The problem was easily mitigated by first writing the Bitmap to a System.IO.MemoryStream, and then to the Response.OutputStream.
using (Bitmap bmp = challenge.RenderImage()) {
using(MemoryStream ms = new MemoryStream()) {
bmp.Save(ms, ImageFormat.Png);
ms.WriteTo(context.Response.OutputStream);
}
}
What I am curious to know is why the original code worked fine locally, but failed on the production server? The reasoning behind the code failing sounds pretty black-and-white to me, so I don't understand why the environment-specific inconsistency could exist at all.
