sane-sharp.5



sane-sharp(5)            SANE Scanner Access Now Easy            sane-sharp(5)


NAME

       sane-sharp - SANE backend for SHARP scanners


DESCRIPTION

       The  sane-sharp  library  implements  a  SANE (Scanner Access Now Easy)
       backend that provides access to  Sharp  SCSI  scanners.   This  backend
       should be considered beta-quality software!  In the current state it is
       known to work with JX-610 and JX-250 scanners. It is prepared for usage
       with  the  JX-330  series scanners, but we are not able to test it with
       these devices.

       For other Sharp scanners, it may or may not work.

       At present, the following scanners are known to work with this backend.

              Vendor  Product id:
              -----   -----------
              Sharp   JX-610
              Sharp   JX-250
              Sharp   JX-320
              Sharp   JX-330
              Sharp   JX-350

       The following scanners are detected by the backend, but not tested:

              Vendor  Product id:
              -----   -----------
              Sharp   JX-325


DEVICE NAMES

       This backend expects device names of the form:

              special

       Where special is either the path-name for the special device that  cor-
       responds  to  a SCSI scanner. The special device name must be a generic
       SCSI device or a symlink to such a device.  Under Linux, such a  device
       name  could be /dev/sga or /dev/sge, for example.  See sane-scsi(5) for
       details.


SCAN OPTIONS

       --mode Scan Mode. Possible settings are: Lineart (1 bit black  &  white
              scans),  Gray  (8 bit gray scale scans), Lineart Color (bi-level
              color scans), and Color (8 bit RGB scans). The default value  is
              Color.

       --halftone-pattern
              Halftone Pattern. Available only for the JX-330 series scanners.
              Possible settings: none, Dither  Bayer,  Dither  Spiral,  Dither
              Dispersed and Error Diffusion.  The default value is none.

       --source
              Paper Source. This option is only available if an automatic doc-
              ument feeder or a transparency adapter  is  installed.  Possible
              settings  are: Flatbed, Automatic Document Feeder, and Transpar-
              ency Adapter.  If an ADF or a transparency adapter is installed,
              using it is the default selection.

       --custom-gamma
              Custom Gamma  This option determines whether a builtin or a cus-
              tom gamma table is used. Possible  settings  are:  yes  (enables
              custom gamma tables) or no (enables a built gamma table).

       --gamma
              Gamma.  This  option is only available if Custom Gamma is set to
              no.  Possible values are: 1.0 or 2.2.  The default value is 2.2.
              (The  JX-250  and  JX-350 have no built in gamma correction; for
              these scanners, a gamma table is downloaded to  the  scanner  by
              the backend.)

       --gamma-table
              Gamma  Table.  Allowed  values:  0..255; 256 numbers must be de-
              fined.  The default values are 0, 1, 2, .. 255 (i.e.,  gamma  ==
              1). This table is only used for gray scale scans.

       --red-gamma-table
              Red Gamma Table. Allowed values: 0..255; 256 numbers must be de-
              fined.  The default values are 0, 1, 2, .. 255 (i.e.,  gamma  ==
              1).

       --green-gamma-table
              Green  Gamma  Table. Allowed values: 0..255; 256 numbers must be
              defined.  The default values are 0, 1, 2, .. 255 (i.e., gamma ==
              1).

       --blue-gamma-table
              Blue  Gamma  Table.  Allowed values: 0..255; 256 numbers must be
              defined.  The default values are 0, 1, 2, .. 255 (i.e., gamma ==
              1).

       --resolution
              Selects  the  resolution  of  the scanned image. Allowed values:
              30..600 (JX-330, JX-350 and JX-610) and 30..400  (JX-250).   The
              default value is 150.

       -l, -t, -x, -y
              Scan  Window.  Top-left x position of scan area (-l), top-left y
              position of scan area (-t), bottom right x position of scan area
              (-x)  and bottom right y position of scan area (-y).  The possi-
              ble settings depend on the scanner model and, for the JX-250 and
              the  JX-350,  also on the usage of the automatic document feeder
              resp. the transparency adapter. Please refer to the  values  al-
              lowed  by  xscanimage(1), or xsane(1).  With scanimage(1), enter
              one of the following commands in order to see the allowed param-
              eter values for the scan window:

              scanimage -d sharp --source "Automatic Document Feeder" --help

              scanimage -d sharp --source Flatbed --help

              scanimage -d sharp --source "Transparency Adapter" --help

       --edge emphasis
              Edge  emphasis.  This option is not available for the JX-250 and
              the JX-350.  Possible settings: None, Middle, Strong, and  Blur.
              The default value is None.

       --threshold
              Sets  the  threshold for black and white pixels in lineart mode.
              Possible values are 1..255.  The default value is 128.  This op-
              tion is only available in scan mode lineart.

       --threshold-red
              Sets  the  threshold for the red component of a pixel in in lin-
              eart color scan mode. Possible values are 1..255.   The  default
              value  is 128.  This option is only available in scan mode color
              lineart.

       --threshold-green
              Sets the threshold for the green component of a pixel in in lin-
              eart  color  scan mode. Possible values are 1..255.  The default
              value is 128.  This option is only available in scan mode  color
              lineart .

       --threshold-blue
              Sets  the threshold for the blue component of a pixel in in lin-
              eart color scan mode. Possible values are 1..255.   The  default
              value  is 128.  This option is only available in scan mode color
              lineart.

       --lightcolor
              Sets the color of the light source. Possible values  are  white,
              red,  green  and blue.  The default value is white.  This option
              is only available in scan modes lineart color and color.


ADF USAGE

       If a paper jam occurrs,  the  maintenance  cover  must  be  opened  and
       closed,  even  if  the  jammed paper can be removed without opening the
       maintenance cover. Otherwise, the error condition will not be cleared.


CONFIGURATION

       The contents of the sharp.conf file is a list  of  options  and  device
       names  that  correspond to Sharp scanners. Empty lines and lines begin-
       ning with a hash mark (#) are ignored.  See  sane-scsi(5)  for  details
       about device names.

       Lines setting an option start with the key word option, followed by the
       option's name and the option's value. At present, three options are de-
       fined: buffers, buffersize, and readqueue.

       Options  defined  at  the start of sharp.conf apply to all devices; op-
       tions defined after a device name apply to this device.

       The options buffers and readqueue are only significant if  the  backend
       has  been  compiled  so  that  for each scan a second process is forked
       (switch USE_FORK in sharp.c ). This process reads the  scan  data  from
       the  scanner  and  writes this data into a block of shared memory.  The
       parent process reads the data from this memory block and delivers it to
       the  frontend.  The  options  control the size and usage of this shared
       memory block.

       option buffers defines the number of buffers used. The smallest  number
       allowed is 2.

       option  buffersize defines the size of one buffer. Since each buffer is
       filled with a single read command sent to the scanner, its size is lim-
       ited  automatically  to  the size allowed by the operating system or by
       the Sane SCSI library for SCSI read commands. A buffer size of  128  kB
       or 256 kB is recommended for scan resolutions of 300 dpi and above.

       option readqueue defines how many read commands to be sent to the scan-
       ner are queued. At present, the Sane SCSI library supports queued  read
       commands  only for for Linux. For other operating systems, option read-
       queue should be set to 0. For Linux, option readqueue should be set  to
       2. Larger values than 2 for option readqueue are not reasonable in most
       cases.  option buffers should be greater than option readqueue.


Performance Considerations

       This section focuses on the problem of stops of the scanner's  carriage
       during a scan. Carriage stops happen mainly with the JX-250. This scan-
       ner has obviously only a small internal buffer compared to  its  speed.
       That means that the backend must read the data as fast as possible from
       the scanner in order to avoid carriage stops.

       Even the JX-250 needs only less than 10 seconds for a 400 dpi  A4  gray
       scale  scan,  which results in a data transfer rate of more than 1.6 MB
       per second. This means that the data produced by the  scanner  must  be
       processed  fairly fast. Due to the small internal buffer of the JX-250,
       the backend must issue a read request for the next data block  as  soon
       as  possible  after  reading a block of data in order to avoid carriage
       stops.

       Stops of the carriage can be caused by the following reasons:

              - too much "traffic" on the SCSI bus
              - slow responses by the backend to the scanner,
              - a program which processes the data acquired by the backend too
              slow.

       Too  much  "traffic" on the SCSI bus: This happens for example, if hard
       disks are connected to the same SCSI bus as the scanner, and when  data
       transfer  from/to  these hard disks requires a considerable part of the
       SCSI bandwidth during a scan. If this is the case, you should  consider
       to connect the scanner to a separate SCSI adapter.

       Slow  responses by the backend to the scanner: Unfortunately, UNIX-like
       operating systems generally have no real time capabilities.  Thus there
       is  no  guarantee  that  the backend is under any circumstances able to
       communicate with the scanner as fast  as  required.  To  minimize  this
       problem,  the  backend  should  be  compiled  so that a separate reader
       process is forked: Make sure that USE_FORK is defined when you  compile
       sharp.c.   If  slow  responses of the backend remain to be problem, you
       could try to reduce the load of the system. Even while the backend  and
       the  reader  process  need only a minor amount of processor time, other
       running processes can cause an increase in the time delay  between  two
       time slices given to the reader process. On slower systems, such an in-
       creased delay can be enough to cause a carriage stop with  the  JX-250.
       For Linux, the usage of the SG driver version 2.1.36 or above is recom-
       mended, because it supports, in combination with the  SCSI  library  of
       Sane  version 1.0.2, command queueing within the kernel.  This queueing
       implementation, combined with a buffer size of at least 128 kB,  should
       avoid most carriage stops.

       Slow  processing of the scan data: An example for this situation is the
       access to the scanner via a 10 MBit Ethernet, which is  definitely  too
       slow  to  transfer  the  scan  data as fast as they are produced by the
       scanner. If you have enough memory available, you can  increase  option
       buffers, so that an entire image can be stored in these buffers.

       In  order to see, if the backend is too slow or if the further process-
       ing of the data is too slow,  set  the  environment  variable  SANE_DE-
       BUG_SHARP  to  1.  When a scan is finished, the backend writes the line
       "buffer full conditions: nn" to stderr. If nn is zero,  carriage  stops
       are  caused  by too slow responses of the backend or too much "traffic"
       on the SCSI bus. If nn is greater than zero, the backend had to wait nn
       times  until  a buffer has been processed by the frontend. (Please note
       that option buffers must be greater than option readqueue in  order  to
       get useful output for "buffer full conditions".)


FILES

       /usr/local/etc/sane.d/sharp.conf
              The backend configuration file.

       /usr/local/lib/sane/libsane-sharp.a
              The static library implementing this backend.

       /usr/local/lib/sane/libsane-sharp.so
              The shared library implementing this backend (present on systems
              that support dynamic loading).


ENVIRONMENT

       SANE_DEBUG_SHARP
              If the library was compiled with debug support enabled, this en-
              vironment  variable  controls  the debug level for this backend.
              E.g., a value of 128 requests all debug output  to  be  printed.
              Smaller levels reduce verbosity.


KNOWN PROBLEMS

       1. ADF Mode
              After  several ADF scans, the scanner moves the carriage back to
              the idle position and back to ADF scan position, before  a  scan
              starts.  We do not know, if this is a problem of the scanner, or
              if this is a bug of the backend. At present,  the  scanner  must
              power off and on to stop this annoying behaviour.

       2. Threshold level does not work (only JX-610)

       3.  The  maximum  resolution  is limited to 600 dpi(JX-610 supported to
       1200 dpi) resp. 400 dpi (JX-250)

       4. If the JX250 is used with an ADF, the following situation can occur:
       After  several  scans,  the scanner moves, after loading a new sheet of
       paper, the carriage to the idle position, and then back to the position
       used  for  ADF  scans.  This happens for every scan, in contrast to the
       calibration, which is done after 10 scans. (For  the  calibration,  the
       carriage  is  also  moved to the idle position.) We do not know if this
       behavior is caused by the backend, or if it is a bug in the firmware of
       the scanner.

       5.  Usage  of a transparency adapter (film scan unit) is supported, but
       not tested.


SEE ALSO

       sane(7), sane-scsi(5)


AUTHORS

       Kazuya Fukuda, Abel Deuring


CREDITS

       The Sharp backend is based on the Canon backend written by Helmut  Koe-
       berle

       Parts of this man page are a plain copy of sane-mustek(5) by David Mos-
       berger-Tang, Andreas Czechanowski and Andreas Bolsch

                                  11 Jul 2008                    sane-sharp(5)

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