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Bug #9017

low-res thumbnail in exported jpeg is incorrect.

Added by Richard Levitte over 7 years ago. Updated about 5 years ago.

Status:
Fixed
Priority:
Low
Category:
General
Target version:
Start date:
10/19/2012
Due date:
% Done:

100%

Estimated time:
Affected Version:
git development version
System:
all
bitness:
hardware architecture:
amd64/x86

Description

I appears that when exporting to jpeg, the low-res thumbnail found in the exif data is a thumbnail of the original image, not of the final image. It's very obvious when a lot of cropping has been done, the picture has been converted to b/w, etc etc etc.

As an example, see the attached image, which is quite heavily cropped and is converted to b/w.

_MG_8785_01.jpg (1.32 MB) _MG_8785_01.jpg (cc-by-nc) Richard Levitte, 10/19/2012 06:54 PM

Related issues

Related to darktable - Bug #8922: OS X Finder shows wrong thumbnails for portrait JPEG images exported by darktableFixed09/09/2012

Associated revisions

Revision 453f2a51 (diff)
Added by Tom Vijlbrief about 5 years ago

[Bug #9017] Fix output of embedded preview in Pentax (k-x) DNG

Revision 354bd659
Added by Pascal de Bruijn about 5 years ago

Merge pull request #921 from tomtor/k-x-preview

[Bug #9017] Fix output of embedded preview in Pentax (k-x) DNG

Revision 8f982477 (diff)
Added by Tom Vijlbrief about 5 years ago

[Bug #9017] Fix output of embedded preview in Pentax (k-x) DNG

(cherry picked from commit 453f2a51bb9066360440d1da42eed1e93ec631c4)

History

#1 Updated by Ulrich Pegelow over 7 years ago

  • % Done changed from 0 to 20
  • Status changed from New to Incomplete

I can not confirm. Please present a clear case: RAW + XMP + exported JPEG.

#2 Updated by Richard Levitte over 7 years ago

#3 Updated by Ulrich Pegelow over 7 years ago

  • % Done changed from 20 to 10
  • Target version set to Future
  • Priority changed from Medium to Low
  • Status changed from Incomplete to Confirmed
  • Category set to General

In fact darktable does not write thumbnails into exported files itself. We seem to inherit thumbs from the input RAW.
I assume that some image viewers have problems as they might take the (then incorrect) thumb for overviews rather
than using the full jpg.

Also darktable seems to stumble over the thumbnail when importing its own generated jpegs:

"Warning: Directory Thumbnail, entry 0x0201: Data area exceeds data buffer, ignoring it."

We need to either find a way to reliably eliminate thumbs (from the exif data) or write our own ones.

#4 Updated by Henrik Andersson over 7 years ago

  • Assignee set to Henrik Andersson

Darktable should discard the thumbnail when fetching the exif blob, this is done
by discarding specific makernotes tags from exif and if thumbnail is there in
exported blob we dont have added the specific makernote parts to be ripped out.

#5 Updated by Richard Levitte over 7 years ago

"I assume that some image viewers have problems as they might take the (then incorrect) thumb for overviews rather
than using the full jpg."

Yup. Among others, the Flickr uploader (on the Flickr web page) shows the low-res thumbnail until it's done uploading the full picture. It's there long enough that one goes "wtf?"...

#6 Updated by Tobias Ellinghaus over 6 years ago

  • System set to all
  • % Done changed from 10 to 20
  • Status changed from Confirmed to Incomplete

I worked in that field some time ago. Could you please verify if this still happens?

#7 Updated by Richard Levitte over 6 years ago

As far as I can see, there are no thumbnails in the exported jpegs. That does solve the problem.

#8 Updated by Tobias Ellinghaus over 6 years ago

  • % Done changed from 20 to 100
  • Status changed from Incomplete to Fixed

Great, then it works as intended. Should someone find previews in our exported images in the future we have to deal with them again. Thing is, manufacturers come up with new places to put previews every other week so we have to play tag with them.

#9 Updated by Tom Vijlbrief about 5 years ago

Pentax K-x DNG files have an embedded preview which gets inserted into the exported jpegs (dt 1.6.4)

Example DNG:

http://tomv.home.xs4all.nl/darktable/IMGP0752.DNG

resulting jpeg (with uncropped preview):

http://tomv.home.xs4all.nl/darktable/IMGP0752.jpg

#11 Updated by Roman Lebedev almost 5 years ago

  • Related to Bug #8922: OS X Finder shows wrong thumbnails for portrait JPEG images exported by darktable added

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