This issue was originally raised by one of the Persian Wikipedia editors. The rationale is that many RTL wikis who share their file repository with a larger LTR wikis will frequently use images that are oriented appropriately for the LTR layout but not the RTL layout. Exapmles are:

(1) Face photos are usually preferred to be look towards the center of the page. In English Wikipedia, for example, photos used in the infoboxes of articles about people usually use images that look to the left. When such an image is not available, one can flip the images horizontally and use that as an alternative, without needing to edit the image externally and re-uploading them.

(2) When such a face photo is shared by many wikis (e.g. when the photo is in Commons, and both English and Arabic Wikipedia's use it), it is inevitable that one of the wikis will end up with the file with the wrong face direction of subject. Having a flipping parameter can fix this.

(3) Same applies to arrows, checkmarks, etc that are on Commons and are used by both LTR and RTL wikis.

Technically speaking, this feature can be implemented as [[File:image.png|flip=horizontally|...]] and it should be easy to implement because we are already using GD/ImageMagick for thumbnailing which has the capability of flipping images too.

From file-name point of view, just as a thumbnail that is resized from original size is named 80px-image.png, a thumbnail that is flipped from original orientation can be named 80px_h-image.png

At the time being, I can't think of a reason why we shouldn't implement vertical flipping as well, although I can't think of a use case either.

Version: unspecified
Severity: enhancement