RE: Introduction to Cryptography I: Encryption (Pt. 4 - Block Ciphers/Modes of Operation)
Well, I'm thinking it's a CBC... with the property that with constant input, the cipher text is 2-periodic, assuming the cipher is applied along the rows of the image.
k(c+v), k(c + k(c+v)), k(c + k(c + k(c + v))...
if k(x) were your block encryption.
k(c+v) = k(c + k(c + k(c + v))
Without any other info, this could happen if your key was x-or'd too... in which case it would flip between k+c+v and v.
Problem with this theory is that it doesn't explain why the stripes would be flat (single colors), unless the same was true of the key and initial vector. And it also doesn't explain why the color would be restored after going through some edges.
I don't know, maybe it's just a plain old ECB? No that's not it, because the same background color in the middle has a different color. I think I'll just wait for you to tell me then.
I know I already said @dexterdev was the closest, but I may have lied. I think you're tied, because his answer is too undercomplicated, and yours is too overcomplicated. You're on the right track there at the end; we'll talk about it in the retrospective next post.
I think @eonwarped did better. Because my answer can even come without reading the article. Just by plain observation, you can answer like mine. @eonwarped has read it properly and knows the stuff I think.