An image composed of multiple images seen simultaneously defines cinema. Just as for painting, it is not necessary that this image be made up of invested images for it to be cinema. A Robert Bresson film is cinema, as is a film composed only of white or black images. One could make a film composed entirely of blue or green images. That would be cinema.
In other words, an image juxtaposed with another, thus giving us a global image made up of juxtaposed local images, is comics. Comics is found in the global image made up of juxtaposed invested local images, and nowhere else. This is the only definition of comics that interests us, and in our eyes it is only comics thus defined that merits being produced.
So, three types of images define three genres: painting, cinema, and comics. When a painter makes a comic the subject of his painting, he is still making a painting. When he works to speak the language of comics, regardless of the techniques he uses, he is making comics. Andy Warhol made comics, but Roy Lichtenstein only made paintings.
It is not the specific content of juxtaposed images that defines comics, but the juxtaposition of the images itself. The text/image dialectic is only secondary in comics; a global image composed of juxtaposed local images without text would still be comics.