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 > > -- > sane-devel mailing list: sane-devel at lists.alioth.debian.org > http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/sane-devel > Unsubscribe: Send mail with subject "unsubscribe your_password" > ? ? ? ? ? ? to sane-devel-request at lists.alioth.debian.org -- "The truth is an offense, but not a sin"
