urgent: how to move and scale textures?

Hi,

I already asked something simular in another thread, but without success.
What I want to achieve, is masking a video with a still image. The still image has an alphachannel, which makes parts of the video visible, and cuts of the rest. (I am drawing this masks in After Effects using a path to generate the mask). This I want to do several times.
In the patch I posted, I am using a method, which works quit good. (you have to load two images with alpha channel to see the effect).

Now: what I REALLY need to do, but don't know how, is to move and scale around the mask-texture and the movie-texture independently.
In my example, it is only possible to move them as a unit, by moving the gridshape.

How do I move/scale textures before applying them to the gridshape?

(I saw an interesting idea here: https://cycling74.com/forums/masking-video-with-jit-gl-gridshape
But in this case, I would be stuck to the few shapes, which can be loaded into gridshape. I have to use my own masks however.)

Thanks for any hint into the right direction!