A way to draw to an image buffer rather than the window.

[kaikalii]

I am currently working on an application that uses rust-sfml for graphics. I want to switch to piston and use piston_window, but my application needs to be able to be able to render to an image buffer rather than a window so that I can save the buffer to a file. The lack of this feature is the one thing keeping me from switching. SFML has a class called RenderTexture, which has exactly this functionality.