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 the path-name for the special device that  corresponds
       to  a  SCSI scanner. The special device name must be a generic SCSI de-
       vice 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 de-
       tails.


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 Trans-
              parency Adapter.  If an ADF or a  transparency  adapter  is  in-
              stalled, 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 para-
              meter 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 lineart
              color scan mode. Possible values are 1..255.  The default  value
              is  128.   This option is only available in scan mode color lin-
              eart.

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

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

       --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 is
              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 JX-250 is used with an ADF, the following situation can oc-
       cur: After several scans, the scanner moves, after loading a new  sheet
       of paper, the carriage to the idle position, and then back to the posi-
       tion  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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