SUMMARY Skanlite will report an incorrect maximum resolution for the scanner (which is an HP ScanJet 3400C): 220 x 296 mm instead of 216 x 297 as stated in the HP support page: https://support.hp.com/us-en/document/bus03735/ The annoyance is that it defaults to "Custom" resolution because A4 is 210 x 297, so Skanlite thinks that this scanner is not able to scan an A4 document, which in reality is able to. Maybe is a conversion error from pixel and ppi to mm? STEPS TO REPRODUCE 1. Starts skanlite 2. read the "Height" box 3. OBSERVED RESULT It says 296 as maximum resolution EXPECTED RESULT It should says 297 SOFTWARE/OS VERSIONS Linux/KDE Plasma: KDE Neon 20.04, all updated (available in About System) KDE Plasma Version: 5.20.5 KDE Frameworks Version: 5.78.0 Qt Version: 5.15.2 ADDITIONAL INFORMATION
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 :)