sane-project-backends/doc/sane-sharp.man

.TH sane\-sharp 5 "11 Jul 2008" "@PACKAGEVERSION@" "SANE Scanner Access Now Easy"
.IX sane\-sharp
.SH NAME
sane\-sharp \- SANE backend for SHARP scanners
.SH DESCRIPTION
The
.B sane\-sharp
library implements a SANE (Scanner Access Now Easy) backend that
provides access to Sharp SCSI scanners.  This backend should be
considered
.B 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.
.PP
For other Sharp scanners, it may or may not work.
.PP
At present,
the following scanners are known to work with this backend.
.RS
.PP
.ft CR
.nf
Vendor  Product id:
-----   -----------
Sharp   JX-610
Sharp   JX-250
Sharp   JX-320
Sharp   JX-330
Sharp   JX-350
.fi
.ft R
.RE
.PP
The following scanners are detected by the backend, but not tested:
.PP
.RS
.ft CR
.nf
Vendor  Product id:
-----   -----------
Sharp   JX-325
.fi
.ft R
.RE
.SH DEVICE NAMES
This backend expects device names of the form:
.PP
.RS
.I special
.RE
.PP
where
.I special
is 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
.I /dev/sga
or
.IR /dev/sge ,
for example.  See
.BR sane\-scsi (5)
for details.

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

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

.TP
.B \-\-source
Paper Source. This option is only available if an automatic document
feeder or a transparency adapter is installed. Possible settings are:
.IR Flatbed ", " "Automatic Document Feeder" ,
and
.IR "Transparency Adapter" .
If an ADF or a transparency adapter is installed, using it is the
default selection.

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

.TP
.B \-\-gamma
Gamma. This option is only available if
.B Custom Gamma
is set to
.IR no .
Possible values are:
.IR 1.0 " or " 2.2 "."
The default value is
.IR 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.)

.TP
.B \-\-gamma\-table
Gamma Table. 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.

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

.TP
.B \-\-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).

.TP
.B \-\-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).

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

.TP
.BR \-l ", " \-t ", " \-x ", " \-y
Scan Window.
Top-left x position of scan area
.RB ( \-l ),
top-left y position of scan area
.RB ( \-t ),
bottom right x position of scan area
.RB ( \-x )
and bottom right y position of scan area
.RB ( \-y ).
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
.BR xscanimage (1),
or
.BR xsane (1).
With
.BR scanimage (1),
enter one of the following commands in order to see the allowed parameter values for
the scan window:

.RS
scanimage \-d sharp \-\-source "Automatic Document Feeder" \-\-help

scanimage \-d sharp \-\-source Flatbed \-\-help

scanimage \-d sharp \-\-source "Transparency Adapter" \-\-help
.RE

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

.TP
.B \-\-threshold
Sets the threshold for black and white pixels in lineart mode.
Possible values are 1..255.
The default value is 128.
This option is only available in scan mode
.IR lineart .

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

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

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

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

.SH ADF USAGE
If a paper jam occurrs, the maintenance cover
.I
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.

.SH CONFIGURATION
The contents of the
.I 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
.BR sane\-scsi (5)
for details about device names.
.PP
Lines setting an option start with the key word
.B option,
followed by the option's name and the option's value. At present, three
options are defined:
.B buffers, buffersize,
and
.B readqueue.
.PP
Options defined at the start of
.I sharp.conf
apply to all devices; options defined after a
device name apply to this device.
.PP
The options
.B buffers
and
.B
readqueue
are only significant if the backend has been compiled
so that for each scan a second process is forked (switch
.B USE_FORK
in
.I 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.
.PP
.B option buffers
defines the number of buffers used. The smallest number allowed is 2.
.PP
.B 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.
.PP
.B 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,
.B option readqueue
should be set to 0. For Linux,
.B option readqueue
should be set to 2. Larger values than 2 for
.B option readqueue
are not reasonable in most cases.
.B option buffers
should be greater than
.B option readqueue.

.SH 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.
.PP
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.
.PP
Stops of the carriage can be caused by the following reasons:
.PP
.RS
\- too much "traffic" on the SCSI bus
.br
\- slow responses by the backend to the scanner,
.br
\- a program which processes the data acquired by the backend too slow.
.PP
.RE
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.
.PP
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
.B USE_FORK
is defined when you compile
.I 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.
.PP
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
.B option buffers,
so that an entire image can be stored in these buffers.
.PP
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
.B SANE_DEBUG_SHARP
to 1. When a scan is finished, the backend writes the line "buffer full
conditions:
.IR nn """
to stderr. If
.I nn
is zero, carriage stops are caused by too slow responses of the backend
or too much "traffic" on the SCSI bus. If
.I nn
is greater than zero, the backend had to wait
.I nn
times until a buffer has been processed by the frontend. (Please note that
.B option buffers
must be greater than
.B option readqueue
in order to get useful output for "buffer full conditions".)

.SH FILES
.TP
.I @CONFIGDIR@/sharp.conf
The backend configuration file.
.TP
.I @LIBDIR@/libsane\-sharp.a
The static library implementing this backend.
.TP
.I @LIBDIR@/libsane\-sharp.so
The shared library implementing this backend (present on systems that
support dynamic loading).
.SH ENVIRONMENT
.TP
.B 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.
.SH KNOWN PROBLEMS
1. ADF Mode
.RS
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.
.RE

2. Threshold level does not work (only JX-610)
.PP
3. The maximum resolution is limited to 600 dpi(JX-610 supported
to 1200 dpi) resp. 400 dpi (JX-250)
.PP
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
.I
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.
.PP
5. Usage of a transparency adapter (film scan unit) is supported, but not
tested.

.SH "SEE ALSO"
.BR sane (7),
.BR sane\-scsi (5)

.SH AUTHORS
Kazuya Fukuda, Abel Deuring

.SH CREDITS
The Sharp backend is based on the Canon backend written by Helmut Koeberle
.PP
Parts of this man page are a plain copy of
.BR sane\-mustek (5)
by David Mosberger-Tang, Andreas Czechanowski and Andreas Bolsch