[KPhotoAlbum] Thumbnails and Images not always correct in Version 4.1.1

[Andreas Neustifter]

Hi Murray!

(I'm writing this from the top of my head, please someone correct me
if necessary...)

On 10 March 2011 14:29, Murray Strome <wmstrome at yahoo.com> wrote:
>
> I have edited a few of the images with the GIMP Photo Editor. Their thumbnails in
> KPA are still those of the original photos, not the changed version. If I click on the
> thumbnail, the image displayed is the edited (changed) version. However, for those
> images that were rotated using GIMP, the thumbnail has the correct orientation (but
> not the other changes made), but when I click on the thumbnail, the image has an
> incorrect orientation.

The handling of thumbnails is as follows: when an image is first added
to KPA a thumbnail is created, this is indexed by the path (or MD5
sum?) of the image, the orientation of the image is baked into the
thumbnail.

When you move images or delete and readd them the thumbnail is for
this image is still in the cache and will be used subsequently.

> [...]
>
> When I was all done, the thumbnails of the affected images are back but they are still
> those of the original, unedited ones, and now with the original (incorrect) orientation.
> When I click on the thumbnail now, however, the image which comes up in the viewer is
> the edited one with the correct orientation.

That is because KPA now knows the correct rotation for the image
itself but still loads the thumbnails from the cache. (And since the
images are "the same" (KPA is pretty good at deducing this) those old
thumbnails are used.)

> In the Konqueror, Nautilus or Dolphin file browsers (with the appropriate view mode), the
> thumbnails are all correct (edited, correct orientation), as is the case with other viewers
> such as Gwenview or Okular.
>
> I wonder from where KPA is getting those original thumbnails, and what I must do to see
> the correct ones.

That is because KPA uses its own thumbnail format since the default
KDE thumbnail cache is too slow for KPA. Thats why most applications
that use the KDE presented ones display them correctly (and those are
recalculated quite liberally) and but KPA uses its own thumbs (which
are preserved much longer).

> Any suggestions? Would it help to send someone a screen shot of the thumbnails as
> seen in KPA and one of the file browsers? Any other information I could include to help?
>
> I really don't know if this is a bug, or just something that I am doing incorrectly.

No, its neither one of those, this behaviour is pretty well
understood, is sort of a feature that can look like a bug (if one does
not know how it works...)

To get proper thumbnails you first have to get proper orientation for
the images: When images are first read into KPA the orientation is
read. If you rotate them inplace you have to reread this information,
you can do this by selecting the images and using the "Reread EXIF
information" (or however its called). In the poping up dialog ensure
that the "Read orientation" checkbox is marked.

To get the proper thumbs you have to rebuild them all, unfortunatelly
there is currently no way to recreate only some of them. To recreate
select the "Rebuild Thumbnails" form somewhere in the menu.

Usually the workflow for people using KPA is to create copies of the
pictures that are edited so that the original is always preserved. KPA
can then stack those images ontop of each other so that they appear as
one unit in KPA. (Its strongly recommended by everyone to never touch
the  originals and always edit copies, see also [1]).

Hope that helps and explains your issues. Please come back to the list
with any questions you have.

Cheers, Andi

[1] http://www.dpbestflow.org/links/38