No doubt this isn't possible but i would like to see if anyone has an ingenious suggestion. We have a third party assembly which can output an image stored internally within a bespoke database to file using an internal method 'SaveToFile', an example:
3rdParty.Scripting.ImageManager man = new 3rdParty.Scripting.ImageManager("ref");
3rdParty.Scripting.Image itemImg = man.GetImage(orderNumber);
Unfortunately unless the 3rd party library provides a
SaveToStream method where you could provide the stream from the outside there's no way to achieve what you are after. You will have to save the contents to a temporary file and then read the contents back.
That's why it's usually best practice when designing a library to provide methods taking Streams as I/O parameters as this would give the consumer the control of whether he wants to save it to a file, memory or network stream.