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Does Win Picture/Fax viewer recompress rotated jpegs?

Posted on 2009-05-04
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Last Modified: 2013-12-25
Hi all,

Quick easy question:

When opening a jpeg photo in Windows Picture and Fax viewer I noticed that sometimes, when I rotate the image,  it seems to save the rotated picture after. My question is:

Has it recompressed the rotated jpeg image when it saves it? If so, have I lost any image quality as a result and how much exactly? or is Windows picture viewer able to just mark some kinda tag in the jpeg to say that it's orientation has changed?

Does the above situation always hold true for a rotated jpeg, or does it only apply when I get the windows message telling me something like "your image is very large and windows cannot  save it without some changes to the image, do you want to proceed?".

Any help much appreciated!
Regards,
Seth.
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Question by:kcs_tec
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by:☠ MASQ ☠
ID: 24293969
Depends on the original.  Picture and Fax Viewer will display a pop-up warning if it is going to have to alter the compression used for any operation but if you hit OK it will replace the saved image with the altered file.

I'll see if I can find the threshold when it does this but certainly if I try to rotate a 5MB image it wants to reduced the quality before altering the orientation.

Otherwise it doesn't use a tag it simply is re-orientated.
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☠ MASQ ☠ earned 100 total points
ID: 24294030
Apparently it's not just files size that determines this. Picture and Fax Viewer will only manage lossless rotation if the image dimensions are multiples of 16 otheriwse you will get some compression - hence the warning pop-up.  This is because Microsoft didn't make it fully compatible with the IJG standard for lossless transformation.

There's a list of software that is IJG compliant here:
http://sylvana.net/jpegcrop/losslessapps.html
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Author Closing Comment

by:kcs_tec
ID: 31577497
Thanks Mate.
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Expert Comment

by:lherrou
ID: 24294185
MASQUERAID is correct. If you want lossless rotation in an easy-to-use viewer program, I recommend IrfanView (http://www.irfanview.com), it's free and easy to use.

Cheers,
LHerrou
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