sane-test - SANE backend for testing frontends
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
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'.
selects the scan mode (Gray or Color).
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
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 one to test whether a
frontend can handle this correctly. This option also enables a fixed width of
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
provides support for changing the order of the
three frames (see option three-pass above). A frontend should support all
sets the resolution of the image in dots per inch.
can be used to simulate an Automatic Document Feeder (ADF).
After 10 scans, the ADF will be "empty".
allows one 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-endianness
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 endianness.
If option read-limit
is set, the maximum amount of data transferred with
each call to sane_read() is limited.
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 timing problems.
enables delaying data to the frontend.
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 statuses.
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.
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).
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.
can be used to print a list of all options to
determines the top-left x position of the scan area.
determines the top-left y position of the scan area.
determines the bottom-right x position of the scan area.
determines the bottom-right y position of the scan area.
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).
(1/6) is a bool test option that has
soft select and soft detect (and advanced) capabilities. That's just a normal
(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
(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.
(4/6) is a bool test option that has soft detect
(and advanced) capabilities. That means the option is read-only.
(5/6) is a Bool test option
that has soft select, soft detect, and emulated (and advanced) capabilities.
(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.
There are 6 int test options in total.
(1/6) is an int test option with no unit and no constraint
(2/6) is an int test option with unit pixel
and constraint range set. Minimum is 4, maximum 192, and quant is 2.
(3/6) is an int test option with unit
bits and constraint word list set.
(4/6) is an int test option with unit mm and
using an array without constraints.
(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.
(6/6) is an int test
option with unit percent and using an array a word list constraint.
There are 3 fixed test options in total.
(1/3) is a fixed test option with no unit and no constraint
(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.
(3/3) is a Fixed test option with no
unit and constraint word list set.
There are 3 string test options in total.
(1/3) is a string test option without constraint.
(2/3) is a string test option with
string list constraint.
(3/3) is a string test option
with string list constraint. Contains some more entries...
(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 <email@example.com>
- config file values aren't tested for correctness