But I got to accuse you of changing horses in midstream,

Then I must tell you that you are wrong. I didn't switch horses at all. Right from the very beginning, I was using the definitions of the terms as they are used in the domain that we were discussing. I invite you to reread all the nodes in the thread now that you understand the context.

If you do so, please note that in my second reply to merlyn, which I wrote the day before you posted a node in this thread at all, I stated, "PNG isn't lossy as long as you define the term 'lossy' in a manner everyone else who talks about compression will understand."

The position you take would be supported be almost any mathematician, but probably few physicists.

That's ridiculous. Most physicists are almost as smart as mathematicians.¹ Certainly they are capable of understanding that jargon is specific to a field of study. ;-)

Seriously, the discussion was about two image formats/compression-algorithms; the accepted terminology for this domain makes a lot of sense. In that context, things like what the image data represents, the resolution of the raw data, or the field of view are simply irrelevant. Those things are decisions made when capturing the image data. The compression algorithm you choose enters the process later, after the bits are collected. (You can't compress bits you don't have.) So, it makes sense to compare the algorithms as they behave with the same input. And, with the same input, JPEG loses information and PNG doesn't. Simple as that.

The term "lossy" as you were speaking of it really applies to the collection phase, not the compression phase of the process. You admit this by claiming you reverted to your physics training. Physics has nothing to do with compression algorithms, but has everything to do with image capture.

In any case, this is a much longer node than I intended and too long for any node buried 12 deep in an old thread. This brings new meaning to "flogging a dead horse."

This is, of course, a tounge in cheek jibe at jepri and nothing more. I'm neither a mathematician nor a physicist and I would have happily written "most mathematicians are as smart as physicists" if jepri's background had been different.

-sauoq
"My two cents aren't worth a dime.";