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

[m. allan noah]

Threshold is only for binary (lineart) images.

allan

On Sat, Apr 14, 2012 at 5:48 AM, Gauthier <gvdmoort at skynet.be> wrote:
> 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
>
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