Right, because it doesn't need to, since that had to have been done in the first place when you picked a width-and-height.

The point you are arguing is completely void of semantic content.

File formats and compression algorithms have nothing to do with the inability to perfectly reproduce a visual scene. That doesn't matter because you couldn't get two people to agree on what a perfect reproduction was anyway. It only matters that you have the ability to capture X bits of information. After you capture those X bits of raw information, you are faced with the problem of storing them and must choose a file format.

If you pick JPEG, you can store that information in less space, but you'll never be able to reproduce your original X bits of information. Hence, we call it "lossy."

If you pick PNG, you can store that information in less space though probably not as little space as you could if you had chosen JPEG. On the other hand, you will be able to reproduce your original X bits of information. Hence, we call it "lossless."

Let's hit the salient points again.

• You can only capture X bits of information.
• If you choose JPEG to store those X bits, you won't be able to get them back again.
• If you choose PNG to store those X bits, you will be able to get them back again.

Hence, we call JPEG "lossy" and PNG "lossless". The accepted terminology is really quite simple.

Yes, collecting real world data is inherently a "lossy" process. No, that's not relevant to discussing the differences between PNG and JPEG which are applied after the data is already collected.

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

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