I have an image as plane imported in Blender 2.91:

Now I want to mask off the red wine and then animate it so it would fill the glas:

Yes, it must be solved in Blender.

Tried it in Compositor with Set Alpha node, but the size of the mask does not fit and the alpha is not correct. Not to mention that I can not figure out how to bring this into shader editor...

Any help very very welcome.

I have an image as plane imported in Blender 2.91:

Now I want to mask off the red wine and then animate it so it would fill the glas:

Yes, it must be solved in Blender.

Tried it in Compositor with Set Alpha node, but the size of the mask does not fit and the alpha is not correct. Not to mention that I can not figure out how to bring this into shader editor...

Any help very very welcome.

Edit:

lehuan5062 had the idea to solve it with a shader: https://blenderartists.org/t/mask-roto-texture-of-image-plane/1278656/4

But still, animated masking in shader editor??