Does Renaming or rotating degrade jpegs?

S
Posted By
Sam
Feb 3, 2005
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257
Replies
4
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Closed
Hi

1)When you rename and save a jpeg (in windowsxp or PSCS) is the image quality degraded?

2)I noticed that Irfanview has a "lossless" rotation function. Does this mean if I
rotate a jpeg in windowsxp or PSCS that there will be loss of image quality (presuming the
rotation is saved)?

3)How many separate (saved) changes can you make with a jpeg before significant
image degradation occurs?

Thanks

Sam
Related Tags
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S
Stephan
Feb 3, 2005
Sam wrote:
Hi

1)When you rename and save a jpeg (in windowsxp or PSCS) is the image quality degraded?\

No
2)I noticed that Irfanview has a "lossless" rotation function. Does this mean if I
rotate a jpeg in windowsxp or PSCS that there will be loss of image quality (presuming the
rotation is saved)?

I believe 90 and 180 degrees do not change anything to your file. If I am wrong, somebody please let us know here

3)How many separate (saved) changes can you make with a jpeg before significant
image degradation occurs?

Depends what you intend to do with your image and how good your eyes are. Try and see by yourself

Stephan
EG
Eric Gill
Feb 4, 2005
Stephan wrote in
news:KbyMd.7224$:

Sam wrote:
Hi

1)When you rename and save a jpeg (in windowsxp or PSCS) is the image quality degraded?\

No

Yes – saving into JPEG *always* degrades an image.

Simply renaming the file from the desktop won’t, of course.

2)I noticed that Irfanview has a "lossless" rotation function. Does this mean if I
rotate a jpeg in windowsxp or PSCS that there will be loss of image quality (presuming the
rotation is saved)?

I believe 90 and 180 degrees do not change anything to your file.

As long as it’s a utility specifically designed for such. If you open it in an image editor first, you’ll lose something re-saving.

If I am wrong, somebody please let us know here

3)How many separate (saved) changes can you make with a jpeg before significant
image degradation occurs?

Depends what you intend to do with your image and how good your eyes are. Try and see by yourself

And the amount of JPEG compression and the contents of image.
S
Sam
Feb 4, 2005
Thanks for reply…see inline
"Eric Gill" wrote in message

Yes – saving into JPEG *always* degrades an image.

You mean from another file format (tif to jpeg) or from another photoeditor (windowsxp explorer to PSCS) ?

Simply renaming the file from the desktop won’t, of course.

You mean from explorer to explorer?

What about using the file browser in PSCS to rename one, or more relevantly, using the batch renaming function which works great?
(batch naming convention sucks in windowsxp. Windows has an "intuitive"option to sort "11" after "9" but this is not respected if using
other photoeditors using the "09" for placing a pic ninth.)

Re Rotation..There was always some myth that if you just rotated 90 to 180 degrees it didnt degrade the image but this didnt make sense to me. It had also been said that rotating within windowsxp/explorer doesnt degrade but not sure if this is true (may be analagous to changing nane within explorer?)
I am puzzled how Irfanview offers lossless rotation (and PSCS does not)

Thanks
Sam
EG
Eric Gill
Feb 4, 2005
"Sam" wrote in
news:NYQMd.147582$:

Thanks for reply…see inline
"Eric Gill" wrote in message

Yes – saving into JPEG *always* degrades an image.

You mean from another file format (tif to jpeg)

No, I mean *every time you save it in JPEG*. It doesn’t matter what it was previously.

Open a JPEG image and re-save it, you get loss. It may be minimal and not noticeable with just one save (depending on compression, the image, and the previous compression), but every time you are not saving the original image but an approximation of it.

or from another
photoeditor (windowsxp explorer to PSCS) ?

Windows XP’s Explorer is file management software, not an image editor.

Simply renaming the file from the desktop won’t, of course.

You mean from explorer to explorer?

No, I mean renaming it. This modifies only the directory entries that refer to the file; the data isn’t touched.

What about using the file browser in PSCS to rename one, or more relevantly, using the batch renaming function which works great?

No, renaming never touches the data.

<snip>

Re Rotation..There was always some myth that if you just rotated 90 to 180 degrees it didnt degrade the image but this didnt make sense to me.

It’s possible to do so by simply shifting the order in the bits that make up the file, and also JPEG has a marker that determines the orientation of the image. Open

It had also been said that rotating within windowsxp/explorer doesnt degrade but not sure if this is true (may be analagous to changing nane within explorer?)

Not even.

As usual, M$ screwed up a fairly simple feature. You should never use Explorer to do any image manipulation of any sort. See:

http://www.dpreview.com/news/0112/01121402nikonxpwarnings.as p

Just to be clear, the warning actually applies to any format image.

I am puzzled how Irfanview offers lossless rotation (and PSCS does not)

But it does – through the file browser. Just don’t open and re-save a JPEG.

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