The sane-test library implements a SANE (Scanner Access Now Easy) back-
       end 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 explic-
       itly.  E.g.  `scanimage -d test' or `xscanimage test'.

       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
       all orders.

       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
       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
       timing problems.

       Option read-delay enables delaying data to the frontend.

       Option read-delay-duration selects the number of microseconds the back-
       ends 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.

       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
       standard error.

       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.

       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.
       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)  capa-
       bilities.  This option can be automatically set by the backend.

       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.   Mini-
       mum 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.

       There are 3 fixed test options in total.

       Option fixed (1/3) is a fixed test option with  no  unit  and  no  con-
       straint set.

       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.

       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.
              ing  all the default values is provided together with this back-
              end.  One  of  the  more  interesting   values   may   be   num-
              ber_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 config-
              uration  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 sepa-
              rator 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

              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 <>

       - config file values aren't tested for correctness

                                  14 Jul 2008                     sane-test(5)
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