Want a GUI composite image where user can slide 1 of 2 component images. Possible?

Just to clarify, I want to display a pair of images that have been superimposed and then allow the user to move one of the images around to align some feature of the images if they want. Is something like this doable?

Some probably useful information on the images: The images will both be black backgrounds with all non-zero pixels having various intensities of a single color (red for one, green for the other), so the composite image should simply be an addition, i.e. if the intensities of a given pixel in each image are the same the composite should show a yellow pixel.