Lossless rotation in PS-7

T
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tacitr
Jun 25, 2004
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I also read that rotations of 90 or 180 degrees done within PS are lossless (actually the statement is that jpeg rotations of those specific magnitudes are lossless.)

If you rotate an image by 90 or 180 degrees, you do not degrade the quality of the image. Rotating by a different amount causes the image to be interpolated; hence, loss occurs.

This has nothing to do with JEPGs. This is all file formats. Rotating an image by an arbitrary amount blurs the image.

Photoshop can not do ANY losless JPEG transformations. If you open a JPEG, do anything to it (even just a Save As), Photoshop re-compresses it, and image quality is lost.

Is there any lossless rotation availably within PS or should I stick with Irfanview for that purpose.

There is lossless rotation. There is no lossless JPEG rotation.

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pixmaker
Jun 26, 2004
I’ve been using another program (Irfanview) to rotate images before editing them in PS-7. I do this because it was my understanding that any image rotation performed by PS was a lossy function.

But now, I read in a tutorial, that I can perform lossless rotation within PS-7 without opening jpeg files through the use of the rotation function within the PS browser.

Also, I read that these PS rotations only affect the thumbnails and not the image file.

I also read that rotations of 90 or 180 degrees done within PS are lossless (actually the statement is that jpeg rotations of those specific magnitudes are lossless.)

I’m confused!

Is there any lossless rotation availably within PS or should I stick with Irfanview for that purpose.

It would sure be nice to handle that operation within PS.

BRAINBLITZ!!!!!

How about opening the jpeg in PS and then simply saving the file in ..psd? Then are not all my subsequent operations and saves lossless?

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Eric Gill
Jun 26, 2004
(Tacit) wrote in m16.aol.com:

Is there any lossless rotation availably within PS or should I stick with Irfanview for that purpose.

There is lossless rotation. There is no lossless JPEG rotation.

The lossless rotation he is referring to is a bit-shifting trick, limited to 90 degree increments, from programs that do not actually open and re- save the file. It is indeed lossless and very handy for digicam files. Very popular among thumbnail programs like ThumbsPlus, IrFanView, and the Browser in PS 7 and later.

Dave, if you open a JPG file in Photoshop for editing, if at no other point you will lose information when you re-save it. If you wish to rotate the image, do so without opening it.
D-
Daemon – eVolution
Jun 28, 2004
Rotating any image format for any degree EXCEPT 90, 180, 270 (you get the idea) will be lossy.

Simple.
N
noone
Jun 28, 2004
In article <cbpe82$tb8$ says
….
Rotating any image format for any degree EXCEPT 90, 180, 270 (you get the idea) will be lossy.

Simple.

Yes they are, however with Bicubic checked and an appropriately high rez file, the loss is not within the realm of noticable. I’ve output triple-truck images that have been rotated to 200lpi offset and not suffered any noticable loss.

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