How to extract separate images from a 3D “.MPO” photo

I need to stash this info somewhere; might as well be well-indexed.

Stereo photos such as those taken by the Nintendo 3DS, with a .MPO file extension, are actually JPEG right-eye images with the left-eye image embedded as extra data. They can be interpreted as JPEG files (perhaps after changing the extension to convince your software to read them), and the left-eye image can be extracted with exiftool, as follows:

exiftool input.mpo -mpimage2 -b > L.jpg

A standalone right-eye image without the extra data can be produced with

exiftool -trailer:all= input.mpo -o R.jpg

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