Reflecta 7200 & Xsane: distortion of scanned images

A user of the French Ubuntu forum has a problem.

To scan old slides and negatives, I acquired a reflecta 7200.
I installed xsane.
During the scan of the photos whether they are vertical or horizontal when taken (but always horizontal in the scanner).
The deformation comes from the fact that there is a 90° rotation.
This causes the image to be compressed and widened at the same time.