[sane-devel] Are "scanimage" options sequence dependent?
jffry at posteo.net
Tue May 15 07:22:20 BST 2018
On 14/05/18 21:11, Dr Rainer Woitok wrote:
> In the first call the "--resolution" option is specified ahead of the
> "--source" option, causing "scanimage" to ignore the former and to use
> the default resolution of 75 dpi. In the second call the "--resolution"
> option is specified after the "--source" option, causing "scanimage" to
> accept it.
> I'm not at all sure whether this is a bug or a feature, but in case of
> the latter the bug is in "man/man1/scanimage.1" which completely fails
> to point out this unexpected behaviour ... :-)
scanimage is not the source of your problem. scanimage simply passes on
the scan options that the backend provides. Many such options depend
upon one another - e.g. if there are options --mode=b&w|grayscale|color
and --depth=1|8|16, then it would make sense for number of depths to be
dependent upon the mode.
If you are only using scanimage then you can only find the dependencies
out by trial and error, using the --help output for each different
combination of options. i.e. the output from:
scanimage --depth=1 --mode=color --help
in my example above is likely to be different from
scanimage --mode=color --depth=1 --help
This is where a GUI like gscan2pdf is useful, as the options are
automatically reloaded when the backend requests it.
BTW, gscan2pdf will also run your favourite open source OCR engine on
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