Bug 431782

Thanks for the report.

Hmm.. strange... exactly this should be fixed in libksane 20.12...
libksane should have a 2mm wiggle room margin for the page sizes... 

can you run 

scanimage -L

to get the device id and then 

scanimage -d <device id> --help

then post the output here.

$ scanimage -L
device `niash:libusb:002:010' is a Hewlett-Packard ScanJet 3400C flatbed scanner

$ scanimage -d niash:libusb:002:010 --help
Usage: scanimage [OPTION]...

Start image acquisition on a scanner device and write image data to
standard output.

Parameters are separated by a blank from single-character options (e.g.
-d epson) and by a "=" from multi-character options (e.g. --device-name=epson).
-d, --device-name=DEVICE   use a given scanner device (e.g. hp:/dev/scanner)
    --format=pnm|tiff|png|jpeg  file format of output file
-i, --icc-profile=PROFILE  include this ICC profile into TIFF file
-L, --list-devices         show available scanner devices
-f, --formatted-device-list=FORMAT similar to -L, but the FORMAT of the output
                           can be specified: %d (device name), %v (vendor),
                           %m (model), %t (type), %i (index number), and
                           %n (newline)
-b, --batch[=FORMAT]       working in batch mode, FORMAT is `out%d.pnm' `out%d.tif'
                           `out%d.png' or `out%d.jpg' by default depending on --format
                           This option is incompatible with --output-file.    --batch-start=#        page number to start naming files with
    --batch-count=#        how many pages to scan in batch mode
    --batch-increment=#    increase page number in filename by #
    --batch-double         increment page number by two, same as
                           --batch-increment=2
    --batch-print          print image filenames to stdout
    --batch-prompt         ask for pressing a key before scanning a page
    --accept-md5-only      only accept authorization requests using md5
-p, --progress             print progress messages
-o, --output-file=PATH     save output to the given file instead of stdout.
                           This option is incompatible with --batch.
-n, --dont-scan            only set options, don't actually scan
-T, --test                 test backend thoroughly
-A, --all-options          list all available backend options
-h, --help                 display this help message and exit
-v, --verbose              give even more status messages
-B, --buffer-size=#        change input buffer size (in kB, default 32)
-V, --version              print version information
Output format is not set, using pnm as a default.

Options specific to device `niash:libusb:002:010':
  Geometry:
    -l 0..220mm (in steps of 1) [0]
        Top-left x position of scan area.
    -t 0..296mm (in steps of 1) [0]
        Top-left y position of scan area.
    -x 0..220mm (in steps of 1) [210]
        Width of scan-area.
    -y 0..296mm (in steps of 1) [290]
        Height of scan-area.
    --resolution 75|150|300|600dpi [150]
        Sets the resolution of the scanned image.
  Image:
    --gamma-table 0..255,... (in steps of 1)
        Gamma-correction table.  In color mode this option equally affects the
        red, green, and blue channels simultaneously (i.e., it is an intensity
        gamma table).
  Scan Mode:
    --mode Color|Gray|Lineart [Color]
        Selects the scan mode (e.g., lineart, monochrome, or color).
  Enhancement:
    --threshold 0..100% (in steps of 1) [inactive]
        Select minimum-brightness to get a white point

Type ``scanimage --help -d DEVICE'' to get list of all options for DEVICE.

List of available devices:
    niash:libusb:002:010

$ dpkg -l | grep sane
ii  libkf5sane-data                                             20.12.1-0xneon+20.04+focal+build11        all          scanner library (data files)
ii  libkf5sane5                                                 20.12.1-0xneon+20.04+focal+build11        amd64        scanner library (runtime)
ii  libsane:amd64                                               1.0.29-0ubuntu5.2                         amd64        API library for scanners
ii  libsane:i386                                                1.0.29-0ubuntu5.2                         i386         API library for scanners
ii  libsane-common                                              1.0.29-0ubuntu5.2                         all          API library for scanners -- documentation and support files
ii  libsane-hpaio:amd64                                         3.20.3+dfsg0-2                            amd64        HP SANE backend for multi-function peripherals
ii  sane-utils                                                  1.0.29-0ubuntu5.2                         amd64        API library for scanners -- utilities

Thanks,

As you can see the backend returns the 296 in stead of the 297 that it should, but it seems the wiggle-room calculation that was added does not work good enough...

The backend does return a wrong value, so it should be fixed there too...

Ok, so should I report a bug against the backend?
May it be sensible to test the scanner on windows to see what dimensions it reports?

The problem is quite probably a conversion rounding error as you wrote.

It would be nice to get the size on windows just as a reference. 

I still need to check why the fix that was done, does not seem to be working for you...

Is it possible to select A4 or is it not in the list? If A4 is in the list but not selected even if you had that set previously I think it is the "saved settings" that needs tweaking.

That said it would be nice if the back-end would return the correct size :)

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Created attachment 135581 [details]
Size in cm

Created attachment 135582 [details]
Size in inches

Created attachment 135583 [details]
Size in pixels

With the original program by HP these are the maximum dimensions reported:

215.9 x 297.2 mm
8.50 x 11.70 in
1700 x 2340 pixels

Thanks for the info!

I checked the source of the niash backend and there the size is hardcoded to 220x296 :{

https://gitlab.com/sane-project/backends/-/blob/master/backend/niash.c

on lines 198 and 199

I'm really astonished that this problem has not been (reported and) fixed before... the backend is from 2001... all the supported scanners have a ~216x297mm area... 

But I will have to check the libksane 2mm wiggle room implementation and check..

Are you able to select A4 or is it totally missing?

It would be nice if you could also report this to https://gitlab.com/sane-project/backends/-/issues to get the root problem fixed.

Regards,
  Kåre

Well, I for one was bothered by this issue for years before reporting it :)

I have reported the issue to sane project: https://gitlab.com/sane-project/backends/-/issues/438

Super!! Thanks :)