How to copy jpegs without degrading the quality

[RVN]

I've read that jpegs involve a lossy type file compression and supposedly degrade each time you copy them. Is this true? Is this measurable? I've copied a jpeg many times over and can't see any degradation.

If I right click and save a jpeg picture and compare it to the one that is recorded in my temporary cache, I can sometimes see a change in that the right clicked saved one is often slightly shrunk.

If you burn jpegs to a CDR and then copy them to another computer and then burn them again on another CDR will you lose quality? I'm concerned with the what they're now saying about the longevity of CDRs, CDs and DVDs. Would zipping them preserve them intact before you burn them without degradation?

Does anybody know? How about opinions?

 

[RussianSoldier]

That doesnt sound right at all.

If you copy a file, it's an exact repica of the original. Each pixel should be the same as the last. The only time I've noticed any major errors with jpegs are when i continually opened them, edited, and saved as another name.

You should be able to burn a jpeg to a cd or dvd as many times as you wish, however I'd suggest using .png if possible, it's becoming more frequent on websites, and the image quality is much better, without huge increases in file size.

 

[par]

word

everyone will have broadband eventually

 

[gsaldivar]

Compound degradation of JPEG files occurs not by copying JPEG files, but by OPENING them and SAVING them.

Each time you OPEN and SAVE a JPEG file, you are decompressing and recompressing a file using a lossy algorithm. Since the lossy JPEG compression algorithm discards slightly different image data each time a new JPEG file is created, each new JPEG file will contain less of the image data of the original file.

Think of this phenomenon like creating a photocopy-of-a-photocopy. Each time you create a new copy, it resembles the original a little less.

Hope this helps!

 

[boshuter]

Originally posted by: gsaldivar
Compound degradation of JPEG files occurs not by copying JPEG files, but by OPENING them and SAVING them.

Each time you OPEN and SAVE a JPEG file, you are decompressing and recompressing a file using a lossy algorithm. Since the lossy JPEG compression algorithm discards slightly different image data each time a new JPEG file is created, each new JPEG file will contain less of the image data of the original file.

Think of this phenomenon like creating a photocopy-of-a-photocopy. Each time you create a new copy, it resembles the original a little less.

Hope this helps!

So, does this mean that every time you play an mp3 it sounds worse than the last time? ( I hope so, I've been telling my friends that I've never heard an mp3 yet that sounds good on a decent stereo:thumbsdown

BTW, jpeg's are the same, if you want quality..... don't use jpeg ( or mp3)

 

[jfunk]

No, it's not "viewing" the image that causes the degredation, it's SAVING it. If you just copy, view, move, etc... the file you aren't changing anything about it, it will always be the same.

But, if you open it and then save it, you are losing data every time you do it. It's the "save" part that loses data, not just looking at it.

And the quality of your MP3's doesn't change either. The quality of the file is whatever it was created as by the person who originally made the file. It doesn't change over time. It's just data, there is nothing physical to degrade here.


j

 

[RVN]

Thanks for clearing that up for me. Almost all of you have been most helpful.