Convert the GraphicsView's Drawable to an image

[GabrieleMessina]

The documentation says it's possible to create an IImage from an IDrawable using the graphicsView.Drawable.ToImage(400, 500) method but IDrawable doesn't declare any ToImage method and even if it did the actual implementation of the class that implements IDrawable should use methods of some other concrete class to achieve this because it doesn't contain any info about the pixel matrix.

Am i getting something wrong? What is the right way to extract an image from a GraphicsView?