Expression painter:image()
returns a Qt variant of class
qt.QImage
representing the drawing surface.
When the underlying surface is a widget without backing store,
this function grabs the widget image from the display.
When the painter operates on a device that cannot be represented
as an image, for instance a printer,
this function returns an empty image for which method
tobool
returns false
.
Note that this function must be invoked without arguments.
Otherwise see the documentation for painter:image(...)
.