Eh, it's sort of the same? You can imagine each pixel as its own message: the point is that repeatedly transforming things in a consistent but "random" way isn'

Eh, it's sort of the same? You can imagine each pixel as its own message: the point is that repeatedly transforming things in a consistent but "random" way isn't actually random. The ciphertext of each pixel is "random", but the pattern when looking at all the pixels is clear.