Loosing quality when rotating image in XP?

[Icarus]

Hi there,

Sorry if this is a double post but sent this an hour ago and it didn't show
up on the server yet. I'm trying to find out for certain whether using the
"rotate clockwise" or
"rotate anti-clockwise" command in WinXP (home), actually degrades quality
or not. There IS a way to rotate jpg images without loosing quality but I'm
not sure if XP does that.

 

[Buggin]

This is the first time that I've heard about this.

I just tested on my workstation and the image remained the same.

besides being vertical or horizontal, image doesn't degrade, IMO

Buggin`

 

[Unknown]

Degrade in what way? On your display? Printed?
Suppose you had a printer that printed 1440 pixels vertically but only 800
horizontally? Would that distort the picture?
Use the same analyses for your display.

 

[Quaoar]

Hi there,

Sorry if this is a double post but sent this an hour ago and it
didn't show up on the server yet. I'm trying to find out for certain
whether using the "rotate clockwise" or
"rotate anti-clockwise" command in WinXP (home), actually degrades
quality or not. There IS a way to rotate jpg images without loosing
quality but I'm not sure if XP does that.

WinXP does not have lossless rotation; but then, neither does Photoshop.
http://bermangraphics.com/coolpix/jpgrotate.htm for a start. Google: jpg
lossless rotation.

Q

 

[Icarus]

Hiya,

This is exactly what I'm talking about. Thanks for the article. It's really
silly that XP doesn't support lossless rotation. That said, I tried rotating
an Image several times and didn't notice any loss in quality. Really weird
thing is that the file size increase when I rotated it the first 90 degs,
then went back when I rotated it again, then increase on the next 90
degs...etc. If XP doesn't do a lossless rotation then how does it manage to
retain almost identical filesize without knowing at what quality rate the
picture was originally encoded.

The worst thing about XP's rotation seems to be that it overwrites the
original EXIF data in the picture.

Anyway for anyone whose interested, I found a free app which does do
lossless rotation and can integrate into the left click menu via an addon
(see the Links section). Check it out: http://www.irfanview.com/

 

[John G.]

The EXIF issues were fixed in XP SP1

http://support.microsoft.com/default.aspx?scid=kb;en-us;323400
Follow the link in the above article to the specific hotfix, and at the
bottom it says fixed in SP1.

 

[Alex Nichol]

Sorry if this is a double post but sent this an hour ago and it didn't show
up on the server yet. I'm trying to find out for certain whether using the
"rotate clockwise" or
"rotate anti-clockwise" command in WinXP (home), actually degrades quality
or not. There IS a way to rotate jpg images without loosing quality but I'm
not sure if XP does that.

You may have to wait 24 hours or so before people see your post - all
round the world.

Repeat answer: JPG is built on a matrix of cells, 8 pixels square. As
long as a picture is a multiple of 8 in both directions (and most are)
they can be rotated 90 degrees without loss. XP's inbuilt rotation will
do this, and if the image is *not* a multiple of 8 will warn you that
there may be a permanent reduction in quality