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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)

NAME | DESCRIPTION | DEVICE NAMES | SCAN OPTIONS | ADF USAGE | CONFIGURATION | Performance Considerations | FILES | ENVIRONMENT | KNOWN PROBLEMS | SEE ALSO | AUTHORS | CREDITS

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