JPEG actually support self-repair: when you save out a JPEG, you can insert "restart markers" every so often, which basically repeat the original headers and al

JPEG actually support self-repair: when you save out a JPEG, you can insert "restart markers" every so often, which basically repeat the original headers and allows a decoder to recover from any corruption. If you put enough restart markers in an image, you can swap or replace the compressed blocks between any given sets of restart markers in the same image without glitching it.