In article , Carlos E.R.
wrote:

Taking it further, what about including each edited image in the file?

making the file huge.

only if done incorrectly.

No way. Say the original is 10 Mb. Each modification saved is another 10
Mb.

that's doing it incorrectly.

the correct way to do it is by saving an edit list and replay it, not
saving a version of the entire image each time.

That's not what the OP said,

he initially wanted a way to confirm that a photo had not been altered,
and the only way to do that is by signing it.

he mentioned including a snapshot at every step. that's a bad idea for
all sorts of reasons.

and needs having the same application for
replaying the steps.

not an issue, and other compatible apps can work.

However, that's an history file. The Gimp saves images that way, undo
works.

saving the undo history in the image is silly. is that gimp's lame
attempt at non-destructive editing because they refuse to do it
correctly? if so, that's laughable.

Ha ha. They are doing it correctly. You are biased.

nope. they aren't doing it at all and have no immediate plans to do so.

they now claim that it might be added in version 3.2 (a change from
their previous claim which was a flat 'no'), except they haven't
figured out how to do it, according to their own road map.

the gimp is a toy, lacking features photoshop had 30 years ago and
*significantly* slower on the same hardware.

Ha ha.

read their roadmap and do some comparisons.