True gray mode is not handled correctly by devices: they have bugs that
lead to incorrect LED color being emitted (e.g. dark red) and thus this
feature is completely unusable. At least LiDE 35/40/50, LiDE 60 and LiDE
80 are affected.
Simpy disabling true-gray unfortunately leads to even worse outcome
because the scanner then simply proceeds to perform a color scan.
To work around these problems we do a normal color scan and then produce
gray output based on the color data. This will satisfy the use cases
when correct gray is needed. In cases when it is sufficient to construct
gray from a single color channel, the color filter setting could be
used.
When sensor exposure values are significantly different from each other
the total scan exposure will be too low leading to the device becoming
confused and significantly
At least on LiDE 50 two-table feeding caused unexplained motor spin-up
failures on certain motor exposures. Various register modifications
showed that there's high likelihood on device-side bug. Even the
official drivers don't use proper two-table feeding.
Brightness and contrast adjustments are handled via gamma tables and
thus gamma functionality is required for these settings to have any
effect.
Previously if the device has a sensor with identity gamma
(gamma = {1, 1, 1}), then gamma tables were turned off, consequently
brightness and contrast settings had no effect.
The underlying issue was identified by Gunnar Hjalmarsson
<gunnarhj@ubuntu.com> and STK.
This was used only on scanners which did not have calibration target
intensity value. All gl841 scanners now have such setting, so the code
can be removed.
True gray mode is not handled correctly by devices: they have bugs that
lead to incorrect LED color being emitted (e.g. dark red) and thus this
feature is completely unusable. At least LiDE 35/40/50, LiDE 60 and LiDE
80 are affected.
Simpy disabling true-gray unfortunately leads to even worse outcome
because the scanner then simply proceeds to perform a color scan.
To work around these problems we do a normal color scan and then produce
gray output based on the color data. This will satisfy the use cases
when correct gray is needed. In cases when it is sufficient to construct
gray from a single color channel, the color filter setting could be
used.
When sensor exposure values are significantly different from each other
the total scan exposure will be too low leading to the device becoming
confused and significantly
At least on LiDE 50 two-table feeding caused unexplained motor spin-up
failures on certain motor exposures. Various register modifications
showed that there's high likelihood on device-side bug. Even the
official drivers don't use proper two-table feeding.
This is not strictly necessary as all known C++ compilers also inject
these types to the global namespace. However this is not guaranteed by
the C++ standard and accordingly some code completion tools don't
support this without additional configuration.
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