[DiThi]

I haven't checked, but I suspect that a better down scaling method can be used while still being compatible with the same decoding algorithm.

[magicalist]

hmm, how could it be? The pixels values have to fit into the eventual reconstructed image. If the values were different than any pixels found in the final image, it wouldn't be progressively loading, it would have several different size images embedded in it.

[DiThi]

(edited) After reading the author's comment above mine, you're very probably right.