How do I copy the entire viewport to a Drawing Canvas?

Hi, I want to 'screencap' my game's viewport during runtime and copy it over to a Drawing Canvas object.

In a nutshell: press a button, game sticks the current frame onto a Drawing Canvas instantly.

I want to do this so I can stick the screen to a certain frame and then manipulate the pixels on the Drawing Canvas to create an effect.

Any help appreciated.