Apply orientation transformation based on EXIF data

[bemyak]

Some images (especially photos) are stored with incorrect orientation. There is a EXIF metadata attached, so browsers and image viewers know how to display it properly.

Unfortunately, when applying transformations, this metadata isn't copied (see image-rs/image#1045 (comment)), so the only way to fix it is to apply the corresponding transform on the Zola's side.

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Sanity check:

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Code changes

• Are you doing the PR on the next branch?
• [?] Have you created/updated the relevant documentation page(s)? (Should I?)

[bemyak]

Just to clarify: all 8 new images are differently oriented, but they have the correct EXIF tag set, so the browser displays them properly. The issue can be reproduced if you try to resize_image any of them (except the first one, it has no rotation).

[Keats]

That seems good. The GH preview shows all image with the top left being red, can you add a detail in one of the test what is the exif data in each?

[bemyak]

The number in an image filename indicates the value of the Orientation tag. For exif_0.jpg the tag is not set. I've added the corresponding descriptions.

For reference, the image description is taken from an output of this command:

$ exiftool -Orientation exif_5.jpg
Orientation                     : Mirror horizontal and rotate 270 CW

You can get the raw value like this:

$ exiftool -b -Orientation exif_5.jpg
5

[Keats]

Small nits.
Do you have an example site where Zola was displaying things incorrectly after an op? Just to easily try this branch somewhere

[bemyak]

Do you have an example site where Zola was displaying things incorrectly after an op? Just to easily try this branch somewhere

Yep, you can clone this, and then open /ru/finland/tuomarilanrinne/ url. The first image (with a baby) is oriented incorrectly, but if you click on it, the original will be opened, which didn't pass the transformation, so it displays correctly.

To build the blog you'll probably need git-lfs installed and zola next, it doesn't build on stable because of #1904

Also when trying different versions remember to delete static/processed_images dir.

[bemyak]

Alternatively, you can just use the test images from this PR, it'll probably be faster. The blog is pretty heavy.

[Keats]

Perfect, thanks!