Capturing screen is only possible on a native iOS/Android level. The Wikitude iOS/Android application does not implement this feature. Have a look at the SDK Sample application (capture screen sample), which is part of the SDK's zip file in order to implement the behaviour in your own application.
about 2 years ago
I am currently using the official wikitude app (available on the app stores), to test my html5 code (with a developer account). Is there any way to trigger photos or screen captures from the code loaded in this app ?