The problem that I have is not that the scanner is not detected. I might
have had that problem long ago but I didn't report it and don't remember
it. The problem I reported in the description of this bug is really that
the pixels scanned are improperly aligned (sometimes called a Shear
transformation). This is the kind of problem that happens when the
number of columns of the image is not counted correctly, such that the
driver and the device disagree on that number but are oblivious about
it. The slope of 1/3 I get means that the driver's image is missing 3
columns compared to what the scanner provides.

Yesterday, I plugged that scanner again for the first time since March
(which is why I only reply now) and then I realised that the problem
happens in 300 dpi, and something worse (lower slope) happens with 600
dpi, but 150 dpi is fine.

The shear is also accompanied by a color offset problem but I didn't
measure it and I suppose that it might be another consequence of the
same bug.

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https://bugs.launchpad.net/bugs/953221

Title:
  UMAX Astra 1220U scanner support stopped working

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