It is impossible using current EasyAR API.
You can take image data out from EasyAR, but there are no interfaces to input image data into EasyAR, both for algorithms and rendering.
We have designed such features and we have some API compatibilities for this. But those features are not ready yet. We still need some time to polish those interfaces (Image, Frame, FrameStreamer, and Buffer which will be introduced in 2.1), especially for all language bindings including Unity.
Back to your question, if you only need to render a new image you created, you do not need EasyAR. EasyAR rendering feature is extremely thin and you can write your own rendering code, for example, if you are using GLES for rendering, it is as simple as drawing two rectangles with a texture image.