sane-test - SANE backend for testing frontends
The sane-test library implements a SANE (Scanner Access Now Easy)
backend that allows testing the SANE installation and SANE frontends.
It provides access to a (nearly) unlimited number of virtual devices.
There is no support for real scanners or cameras. However, the backend
simulates scanning and setting options.
The idea is not only to find bugs in frontends but also to show all
capabilities of SANE. Therefore sane-test implements functions and
options that are not (or seldom) found in other backends.
The backend is commented out in /etc/sane.d/dll.conf, so either the
comment character must be removed or the backend must be called
explicitly. E.g. ‘scanimage -d test’ or ‘xscanimage test’.
SCAN MODE OPTIONS
Option mode selects the scan mode (Gray or Color).
Option depth determines the number of bits per sample (1. 8, or 16).
Keep in mind, that this value refers to the sample, not the pixel. So
depth=16 results in 48 bits per pixel in color mode. The most usual
combinations are mode=Gray, depth=1 for lineart, mode=Gray, depth=8 for
gray and mode=Color, depth=8 for color mode. The combination of color
and 1-bit mode is quite obscure (8 colors) but allowed in the SANE
standard. However, the meaning of bits is not defined. Currently 1 =
high intensity and 0 = low intensity is used.
Setting option hand-scanner results in the test-backend behaving like a
hand-scanner. Hand-scanners do not know the image height a priori.
Instead, they return a height of -1. Setting this option allows to
test whether a frontend can handle this correctly. This option also
enables a fixed width of 11 cm.
Setting option three-pass simulates a three-pass scanner. Older color
scanners needed to scan the image once per color (reg/green/blue) to
get the full image. Therefore, in this mode three single frames are
transmitted in color mode.
Option three-pass-order provides support for changing the order of the
three frames (see option three-pass above). A frontend should support
Option resolution sets the resolution of the image in dots per inch.
Option source can be used to simulate an Automatic Document Feeder
(ADF). After 10 scans, the ADF will be "empty".
Option test-picture allows to set the image that’s returned to the
frontend. While "Solid white" and "Solid black" are quite obvious, the
other options need some more explanation. Color patterns are used to
determine if all modes and their colors are represented correctly by
the frontend. The grid should look like the same in every mode and
resolution. A table of all the test pictures can be found at:
If option invert-endianess is set, the upper and lower bytes of image
data in 16 bit modes are exchanged. This option can be used to test
the 16 bit modes of frontends, e.g. if the frontend uses the correct
If option read-limit is set, the maximum amount of data transferred
with each call to sane_read() is limited.
Option read-limit-size sets the limit for option read-limit. A low
limit slows down scanning. It can be used to detect errors in frontend
that occur because of wrong assumptions on the size of the buffer or
Option read-delay enables delaying data to the frontend.
Option read-delay-duration selects the number of microseconds the
backends waits after each transfer of a buffer. This option is useful
to find timing-related bugs, especially if used over the network.
If option read-return-value is different from "Default", the selected
status will be returned by every call to sane_read(). This is useful
to test the frontend’s handling of the SANE statii.
If option ppl-loss is different from 0, it determines the number of
pixels that are "lost" at the end of each line. That means, lines are
padded with unused data.
Option fuzzy-parameters selects that fuzzy (inexact) parameters are
returned as long as the scan hasn’t been started. This option can be
used to test if the frontend uses the parameters it got before the
start of the scan (which it shouldn’t).
Option non-blocking determines if non-blocking IO for sane_read()
should be used if supported by the frontend.
If option select-fd is set, the backend offers a select filedescriptor
for detecting if sane_read() will return data.
If option enable-test-options is set, a fairly big list of options for
testing the various SANE option types is enabled.
Option print-options can be used to print a list of all options to
Option tl-x determines the top-left x position of the scan area.
Option tl-y determines the top-left y position of the scan area.
Option br-x determines the bottom-right x position of the scan area.
Option br-y determines the bottom-right y position of the scan area.
BOOL TEST OPTIONS
There are 6 bool test options in total. Each option is numbered.
(3/6) means: this is option 3 of 6. The numbering scheme is intended
for easier detection of options not displayed by the frontend (because
of missing support or bugs).
Option bool-soft-select-soft-detect (1/6) is a bool test option that
has soft select and soft detect (and advanced) capabilities. That’s
just a normal bool option.
Option bool-hard-select-soft-detect (2/6) is a bool test option that
has hard select and soft detect (and advanced) capabilities. That
means the option can’t be set by the frontend but by the user (e.g. by
pressing a button at the device).
Option bool-hard-select (3/6) is a bool test option that has hard
select (and advanced) capabilities. That means the option can’t be set
by the frontend but by the user (e.g. by pressing a button at the
device) and can’t be read by the frontend.
Option bool-soft-detect (4/6) is a bool test option that has soft
detect (and advanced) capabilities. That means the option is read-
Option bool-soft-select-soft-detect-emulated (5/6) is a Bool test
option that has soft select, soft detect, and emulated (and advanced)
Option bool-soft-select-soft-detect-auto (6/6) is a Bool test option
that has soft select, soft detect, and automatic (and advanced)
capabilities. This option can be automatically set by the backend.
INT TEST OPTIONS
There are 6 int test options in total.
Option int (1/6) is an int test option with no unit and no constraint
Option int-constraint-range (2/6) is an int test option with unit pixel
and constraint range set. Minimum is 4, maximum 192, and quant is 2.
Option int-constraint-word-list (3/6) is an int test option with unit
bits and constraint word list set.
Option int-constraint-array (4/6) is an int test option with unit mm
and using an array without constraints.
Option int-constraint-array-constraint-range (5/6) is an int test
option with unit mm and using an array with a range constraint.
Minimum is 4, maximum 192, and quant is 2.
Option int-constraint-array-constraint-word-list (6/6) is an int test
option with unit percent and using an array a word list constraint.
FIXED TEST OPTIONS
There are 3 fixed test options in total.
Option fixed (1/3) is a fixed test option with no unit and no
Option fixed-constraint-range (2/3) is a fixed test option with unit
microsecond and constraint range set. Minimum is -42.17, maximum
32767.9999, and quant is 2.0.
Option fixed-constraint-word-list (3/3) is a Fixed test option with no
unit and constraint word list set.
STRING TEST OPTIONS
There are 3 string test options in total.
Option string (1/3) is a string test option without constraint.
Option string-constraint-string-list (2/3) is a string test option with
string list constraint.
Option string-constraint-long-string-list (3/3) is a string test option
with string list constraint. Contains some more entries...
BUTTON TEST OPTION
Option button (1/1) is a Button test option. Prints some text...
The backend configuration file (see also description of
SANE_CONFIG_DIR below). The initial values of most of the basic
SANE options can be configured in this file. A template
containing all the default values is provided together with this
backend. One of the more interesting values may be
number_of_devices. It can be used to check the frontend’s
ability to show a long list of devices. The config values
concerning resolution and geometry can be useful to test the
handling of big file sizes.
The static library implementing this backend.
The shared library implementing this backend (present on systems
that support dynamic loading).
This environment variable specifies the list of directories that
may contain the configuration file. Under UNIX, the directories
are separated by a colon (‘:’), under OS/2, they are separated
by a semi-colon (‘;’). If this variable is not set, the
configuration file is searched in two default directories:
first, the current working directory (".") and then in
/etc/sane.d. If the value of the environment variable ends with
the directory separator character, then the default directories
are searched after the explicitly specified directories. For
example, setting SANE_CONFIG_DIR to "/tmp/config:" would result
in directories "tmp/config", ".", and "/etc/sane.d" being
searched (in this order).
If the library was compiled with debug support enabled, this
environment variable controls the debug level for this backend.
Higher debug levels increase the verbosity of the output.
Example: export SANE_DEBUG_TEST=4
Henning Meier-Geinitz <firstname.lastname@example.org>
- config file values aren’t tested for correctness
14 Jul 2008 sane-test(5)