Fix image orientation when generating thumbnail

[prodrigestivill]

Add EXIF rotation before generating thumbnails.

Fixes matrix-org/matrix-spec-proposals#2384, matrix-org/matrix-spec#292, element-hq/element-web#1999, and element-hq/element-web#2059

For now it needs pillow>=4.3.0.
It can be moved to use Image.getexif() instead of Image._getexif() but it will require pillow>=6.0.0.
This is explained in Pillow 6.0.0 Documentation.

Not sure if the preference is to use the oldest minimum libraries or no issues at all with using latest ones.

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file
• Pull request includes a sign off

[prodrigestivill]

Afects matrix-org/matrix-doc#483

[codecov]

Codecov Report

Merging #5039 into develop will decrease coverage by 0.01%.
The diff coverage is 38.09%.

@@             Coverage Diff             @@
##           develop    #5039      +/-   ##
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- Coverage    62.15%   62.13%   -0.02%     
===========================================
  Files          336      336              
  Lines        34688    34709      +21     
  Branches      5683     5687       +4     
===========================================
+ Hits         21559    21567       +8     
- Misses       11593    11604      +11     
- Partials      1536     1538       +2

[anoadragon453]

Looks good otherwise, but we'll need to see if this is the approach we want to take.

[prodrigestivill]

Looks good otherwise, but we'll need to see if this is the approach we want to take.

The main problem with current Thumbnailer is that creates an scaled or cropped thumbnail and throws away the EXIF orientation information.
So either rotate before the scale/crop or copy the EXIF orientation information when generating the thumbnail.

So for me this problem is independent of what is decided in matrix-org/matrix-doc#483 but it still affects to solve the whole problem.

But it can still be decied to copy the EXIF orientation in the thumbnail instead, but I think this would be an strange solution.

[richvdh]

apart from a bit of nitpicking, the code looks reasonable.

However, it seems like it is making a particular decision on https://github.com/matrix-org/matrix-doc/issues/483. It may be a valid decision, but the discussion should happen on that issue, not here.

So please can you make your case on that issue?

[richvdh]

Thanks again for this.

I have a few requests for minor changes; it otherwise looks good.

[richvdh]

Ok, this looks good, thanks.

Sadly it's failing a couple of checks when I run it against the CI. Can you investigate and fix, please?

[richvdh]

oh urgh the isort failure is something that is fixed in develop. Could you merge in latest develop? sorry, but the rest of the CI won't run until it's fixed.

[richvdh]

lgtm!

(please avoid force-pushing in general: it makes it hard to see how the PR has been changed since a previous review)

[johansmitsnl]

Should this be working in the latest docker image? For me it is not working.

[prodrigestivill]

It should be working on latest official Docker image.

Please ensure you are looking at the thumbnail is generated by the sever and not the thumbnail generated by the client or the thumbnail of the thumbnail generated by the client.

Normally Matrix clients generate their own thumbnails and upload them without any EXIF information.