Savageduck
For example, you can add sharpening with a high pass sharpen tool to an image, save it as a JPEG, send it to someone else, and they can use a blur tool to reverse the sharpen.

If the sharpening is done with UnsharpMask that cannot be done. USM is not reversible.âEUR

Floyd L. Davidson
And that is true!

Eric Stevens
I understood him to be saying that inspite of the losses of a JPEG conversion, recovery of the original sharpness is possible if the original sharpening process used a high pass filter. That while saving as a JPEG will always cause losses, this will not prevent a Gaussian blur operation from recovering the sharpness of the original image.

Floyd L. Davidson
Again, that is extremely close but lets not suggest that the "sharpness of the original image" is *fully* recovered. In other words "sharpness of the original image" is not the same as "original sharpness".

Savageduck
So, it isnâEUR(Tm)t a fully reversible and/or non-destructive process?

Floyd L. Davidson
I've never claimed it was in any way a "non-destructive process".

Reversible does not necessarily mean revertable from one specific state to another specific previous state. It means incremental variation is incrementally reversed. How far it can be taken is another matter.

Savageduck
BTW: Nothing personal, but your Usenet client seems to have a problem with Unicode (UTF8) text encoding,

Floyd L. Davidson
Nothing personal, but Usenet is an ascii text medium.