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> Lossless Jpeg Rotation Problem
GDC
post Jul 2 2007, 03:14 AM
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Member No.: 2,457



PMView is a great image viewer I'm using for years now.

The "lossless JPEG rotation" is a great feature, but now I'm having a problem
with it. Camera's that have an orientation sensor indicate the orientation of
the image via the ID 0112H and PMView honors it correctly when displaying the image.
Not all softwares honor that tag however.

You can for example find pictures on the web that are not oriented correctly
as the user does not know about that feature and saw the picture turned
correctly on its PC.

When rotating an image, PMView does not change the tag, so softwares that
honor the tag display the image wrongly afterwards. PMView should change the
tag also. I further investigated this, and it seems to me that there is only
one good solution to make all other softwares display the image correctly,
namely to change the tag to 0001H (Top-Left), whatever rotation is applied.
Indeed, as the software can't know what's the top of the image, it is up to
the user to rotate until the image displays correctly. All softwares will
then display the image like seen with PMView.

Another addition could be an option to allow the user to choose whether the
tag is honored or not. That way, one can see the pictures that should be
rotated before sending them to a software that does not honor the tag.
A daily tip could furthermore explain how to handle rotation for all situations
(set auto-rotate switch off, select all rotated pictures in open panel, and
run lossless rotate).

I did not investigate what has to be done with the thumbnail image in the file
when it's present. Should be handled similarly I guess.

Regards
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Peter
post Jul 8 2007, 11:07 AM
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Posts: 661
Joined: 14-March 00
From: Wilmington, North Carolina
Member No.: 3



Check out the lossless rotation options. They should correctly update the tag.

The problem with different applications can be solved, and PMView has a builtin conversion function for this very purpose: Use "JPEG rotate lossless using EXIF information" to rotate an image so that its orientation is normalized and shows correctly in all browsers.

Note that you can select a bunch of images in the File Open dialog and right click to do this operation on several images at once.


--------------------
Peter Nielsen (peter@pmview.com) "If you can dream it, you can do it" JFK.
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