[sane-devel] HP 2300C: impossible to get extras functionnalities from scanimage

[Gauthier]

Hello,

I'm using sane-utils 1.0.22-7 on a debian testing, and my scanner is
an HP scanjet 2300c, that seems correctly detected:

  $ scanimage -L
  device `genesys:libusb:002:002' is a Hewlett Packard ScanJet 2300c flatbed scanner
  $ scanimage -h
    [...]
    Enhancement:
      --custom-gamma[=(yes|no)] [no]
          Determines whether a builtin or a custom gamma-table should be used.
      --gamma-table 0..16383,... [inactive]
          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).
      --red-gamma-table 0..16383,... [inactive]
          Gamma-correction table for the red band.
      --green-gamma-table 0..16383,... [inactive]
          Gamma-correction table for the green band.
      --blue-gamma-table 0..16383,... [inactive]
          Gamma-correction table for the blue band.
    Extras:
      --lamp-off-time 0..60 [15]
          The lamp will be turned off after the given time (in minutes). A value
          of 0 means, that the lamp won't be turned off.
      --threshold 0..100% (in steps of 1) [50]
          Select minimum-brightness to get a white point
      --threshold-curve 0..127 (in steps of 1) [50]
          Dynamic threshold curve, from light to dark, normally 50-65
      --disable-dynamic-lineart[=(yes|no)] [inactive]
          Disabel use of a software adaptative algorithm to generate lineart
          instead of relying on hardware lineart
      --disable-interpolation[=(yes|no)] [no]
          When using high resolutions where the horizontal resolution is smaller
          than the vertical resolution this disables horizontal interpolation.
      --color-filter Red|Green|Blue [Green]
          When using gray or lineart this option selects the used color.

The problem is that the options --threshold and --threshold-curve
doesn't seem to change anything; I've tried with extreme values, I
don't see any change in the resulting images, and when the command
is running, the min/max graylevels doesn't change much:

  gv at fantasio:~$ scanimage -v  -x 95 -y 70  --format=tiff >image.tiff
  scanimage: scanning image of size 1122x826 pixels at 8 bits/pixel
  scanimage: acquiring gray frame
  scanimage: min/max graylevel value = 24/245
  scanimage: read 926772 bytes in total
  gv at fantasio:~$ scanimage -v  -x 95 -y 70 --threshold 10 --format=tiff
  >image2.tiff
  scanimage: scanning image of size 1122x826 pixels at 8 bits/pixel
  scanimage: acquiring gray frame
  scanimage: min/max graylevel value = 33/244
  scanimage: read 926772 bytes in total
  gv at fantasio:~$ scanimage -v  -x 95 -y 70 --threshold 90 --format=tiff
  >image2.tiff
  scanimage: scanning image of size 1122x826 pixels at 8 bits/pixel
  scanimage: acquiring gray frame
  scanimage: min/max graylevel value = 33/245
  scanimage: read 926772 bytes in total
  gv at fantasio:~$ scanimage -v  -x 95 -y 70 --threshold-curve 0
  --format=tiff >image3.tiff
  scanimage: scanning image of size 1122x826 pixels at 8 bits/pixel
  scanimage: acquiring gray frame
  scanimage: min/max graylevel value = 33/245
  scanimage: read 926772 bytes in total
  gv at fantasio:~$ scanimage -v  -x 95 -y 70 --threshold-curve 127
  --format=tiff >image3.tiff
  scanimage: scanning image of size 1122x826 pixels at 8 bits/pixel
  scanimage: acquiring gray frame
  scanimage: min/max graylevel value = 33/247
  scanimage: read 926772 bytes in total

More annoying, I can't get other than a full black image when I try to
use custom gamma:

  gv at fantasio:~$ scanimage -v -v -x 95 -y 70 --custom-gamma=yes
  --gamma-table `gamma4scanimage 0.7` --format=tiff >image4.tiff
  scanimage: scanning image of size 1122x826 pixels at 8 bits/pixel
  scanimage: acquiring gray frame
  scanimage: min/max graylevel value = 0/3
  scanimage: read 926772 bytes in total
  Closing device
  Calling sane_exit
  scanimage: finished

As you can see, the min/max graylevel values are then minimal :-(
All other combinations of -gamma-table give the same result.

Any Ideas ?

Thanks in advance,
-- 
Gauthier