A "movie barcode" is all the frames of a movie smashed together into one image, as seen on this incredible Tumblr.
It's a great way to get a quick glance at the color scheme of a movie. For example, this is every frame of The Empire Strikes Back in one image. Notice all the blues and whites toward the beginning on Hoth, leading to dark greens, browns, and blacks on Dagobah and in space, followed by the lighter colors of Cloud City.