Today Roger N. Clark (change username to rnclark) spoke these
views with conviction for everyone's edification:

Would you or anyone just lurking be at all interested in
my posting the full text of the several E-mails I
exchanged with the fellow who did those 1,600% image
increase's of my Mt.Suribachi picture?

Perhaps you might glean something useful that I didn't and
clear this up. We'd all learn something in the process,
maybe...


Why not post them here?

Yes, /here/...They're just text, I was just trying to gauge
interest as the task isn't trivial...I've got to find them
again, and reformat for best readibility and keep things in
chronological order so people can follow what was said to who
by whom.

I've looked at the images posted in the alt.binaries group,
and find the enlargement job VERY good. It is not
something that can be done in photoshop (CS2), at least not
anything simple. I do see artifacts, but every method has
artifacts.

Roger, enlarging or shrinking do not create artefacts to the
strict definition of the term. These are blobs, streaks,
spots, etc. near sharp corners and often on broad expanses of
color or even brightness/contrast, and are caused almost
excluively by the lossy nature of JPEG compression.

In the 618 x 479 original scan that I posted, that I have no
way of knowing who did it or how it was done or when, but is
readily available in numerous web sites, it is likely that the
image was saved, possibly edited and/or resized, then saved
again back to JPEG, perhaps many times. Each time you do that,
the damage gets worse until the image is just so much mush.

Unless the original scanner just plain didn't know what they
were doing, there wouldn't be any artefacts in a BMP or TIFF,
but there well might be jaggies...

--
ATM, aka Jerry