Interp a list/matrix into a bigger list/matrix

Hi everyone, newbie here.
In the attached patch you'll see a little 3x3 matrix (on the right) created with three 9-numbers lists.
I can add interp_1 to the right pwindow to obtain an interpolated view.

On the left you can load a frame (png in the folder), and then the middle great pwindow shows the mix of the frame + the colors.

Now, I like to see the frame perfectly defined, but I'd like to see interpolated colors instead of the neat square in the center! (I can understand it happens because the great pwindow take spatial definition from the frame png.)

Is it possible to mix the two images having interpolated colors?

(I thought I could achieve it by interpolating the 3x3 matrix into a bigger 300x300 matrix, but I don't know how...)

Thanks a lot.