Sandman
In article <87k34zrs9f.fld@barrow.com>, Floyd L. Davidson wrote:

Eric Stevens
Unfortunately he knows too much, compared with the rest of us. I did wonder when he threw in that JPEG conversion but I finally he concluded that he was trying to make a point.

Floyd L. Davidson
I'll have to admit that when I used JPEG as an example format it just never occurred to me that anyone would try to argue the absurd point this discussion has taken. I did not suggest JPEG formatting was not lossy or that it was reversible, in any way. I did say that sharpen is reversible and unsharp mask is not.

Sandman
The point we're making fun of is that you did add a lossy middle step to your claim about the first process being reversed by the third process with a lossy process in the middle.

If you knew anything about image processing, you wouldn't have added a lossy process in the middle and the claim that steps taken before it could be reversed. But here we are.

Eric Stevens
You can't do that if the original sharpening was USM as it is not fully reversible.

Floyd L. Davidson
That is exactly the point. It just is not reversible.

Sandman
That is, if you're using antique software and know nothing about modern software, in which case everything is 100% reversible. But hey, that's life on a 486 PC running ancient linux.