Provided by: libsane_1.0.19-23ubuntu7_i386 bug

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
       corresponds 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

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

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

       Paper Source (parameter --source for scanimage). This  option  is  only
       available, if an automatic document feeder or a transparency adapter is
       installed. Possible settings:
              Flatbed
              Automatic Document Feeder
              Transparency Adapter
       If an ADF or a transparency adapter  is  installed,  using  it  is  the
       default selection.

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

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

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

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

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

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

       Resolution  in  pixel  per inch (parameter --resolution for scanimage).
       Selects the resolution of the scanned image. Allowed values:
              30..600 (JX-330, JX-350 and JX-610) resp.  30..400 (JX-250)
       The default value is 150.

       Scan Window

       The possible 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  allowed  by
       xscanimage,  or  xsane.  With  scanimage,  enter  one  of the following
       commands:

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

              scanimage -d sharp --source Flatbed --help

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

       in order to see the allowed parameter values for the scan window.

       The scan window parameters are:

              Top-left x position of scan area (parameter -l for scanimage);
              Top-left y position of scan area (parameter -t for scanimage);
              bottom  right  x  position  of  scan  area  (parameter  -x   for
              scanimage);
              bottom   right  y  position  of  scan  area  (parameter  -y  for
              scanimage);

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

       Threshold (parameter --threshold for scanimage). Sets the threshold for
       black and white pixels in lineart mode. Possible values:
              1..255
       The default value is 128.  This option is only available in  scan  mode
       lineart.

       Threshold  Red  (parameter  --threshold-red  for  scanimage).  Sets the
       threshold for the red component of a pixel in  in  lineart  color  scan
       mode. Possible values:
              1..255
       The  default  value is 128.  This option is only available in scan mode
       color lineart.

       Threshold Green (parameter --threshold-green for scanimage).  Sets  the
       threshold  for  the green component of a pixel in in lineart color scan
       mode. Possible values:
              1..255
       The default value is 128.  This option is only available in  scan  mode
       color lineart.

       Threshold  Blue  (parameter  --threshold-blue  for scanimage). Sets the
       threshold for the blue component of a pixel in in  lineart  color  scan
       mode. Possible values:
              1..255
       The  default  value is 128.  This option is only available in scan mode
       color lineart.

       Light Color (parameter --LightColor for scanimage). Sets the  color  of
       the light source. Possible values:
              white
              red
              green
              blue
       The  default  value  is  white.   This option is only available in scan
       modes lineart color and color.

ADF USAGE

       If a paper jam occurred, 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 cannot 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
       beginning 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
       defined: buffers, buffersize, and readqueue.

       Options  defined  at  the  start  of  sharp.conf  apply to all devices;
       options 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
       limited 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
       scanner are queued. At present, the Sane SCSI library  supports  queued
       read  commands  only for for Linux. For other operating systems, option
       readqueue 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
       scanner 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
       increased 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
       recommended, 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
       processing of the data  is  too  slow,  set  the  environment  variable
       SANE_DEBUG_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

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

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

       /usr/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
              environment  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
       Koeberle

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