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) back-
end 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 de-
vices.
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 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 Dis-
persed and Error Diffusion. The default value is none.
--source
Paper Source. This option is only available if an automatic docu-
ment feeder or a transparency adapter is installed. Possible set-
tings are: Flatbed, Automatic Document Feeder, and Transparency
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 cus-
tom 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 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
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 de-
fined. 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 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(1), or xsane(1). With scanimage(1), enter one of the
following commands in order to see the allowed parameter 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 lineart
.
--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 beginning
with a hash mark (#) are ignored. See sane-scsi(5) for details about de-
vice 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; 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 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 com-
municate 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 re-
duce 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 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 scan-
ner. 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/x86_64-linux-gnu/sane/libsane-sharp.a
The static library implementing this backend.
/usr/lib/x86_64-linux-gnu/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 occur:
After several scans, the scanner moves, after loading a new sheet of pa-
per, 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 cal-
ibration, which is done after 10 scans. (For the calibration, the car-
riage is also moved to the idle position.) We do not know if this behav-
ior 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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