NAME

       minidjvu - encode/decode black-and-white DjVu pages

SYNOPSIS

       minidjvu  [options] input_file output_file

       There is a similar syntax for multipage compression:

       minidjvu  [options] input_files output_file

       See MULTIPAGE ENCODING section below for more details.

DESCRIPTION

       minidjvu encodes and decodes single-page black-and-white DjVu files.

       minidjvu is derived from DjVuLibre, which is the primary support library for DjVu.

       Besides  bitonal  DjVu,  minidjvu  understands Windows BMP, PBM and TIFF (through libtiff)
       formats.  Both inputfile and outputfile may be BMP, PBM, TIFF or DjVu. The  file  type  is
       determined by extension.  Input and output may coincide.

       When  given  a DjVu-to-DjVu job, minidjvu decodes, then re-encodes the image.  DjVu layers
       other than bitonal picture are lost.

       Specifying a bitmap-to-bitmap job is possible, but relatively useful  only  with  --smooth
       option.

       All  options  preceded  by  two hyphens can be used with one hyphen.  This is done to make
       minidjvu interface more familiar for DjVuLibre users.

MULTIPAGE ENCODING

       To activate the multipage mode either specify in your command  line  more  than  just  one
       input  file,  or  pass  to  minidjvu  a  single  multipage  tiff  document. By default (if
       --indirect is not specified) the  compressed  pages  are  stored  into  a  single  bundled
       document under the name provided in the command line.

       There are several options referring to the multipage encoding process, namely --pages-per-
       dict, --indirect and --report.

OPTIONS

       -A

       --Averaging
              Compute "average" representatives for shapes matching a pattern.

       -a n

       --aggression n
              Sets aggression for pattern matching. The more the aggression, the  less  the  file
              size,  but  the  more  likely  substitution  errors will occur. The default is 100.
              Usually you can raise it to about 110 more or less safely. Probably even  200  will
              work fine, but don't rely on that.

              Consistent  aggression  levels  between  versions  is not guaranteed.  The default,
              however, will always be 100.

              This option turns on --match automatically.

       -c

       --clean
              Remove small black marks that  are  probably  noise.   This  algorithm  can  really
              devastate halftone patterns, so use with caution.

              This option is turned on by --lossy.

       -d n

       --dpi n
              Specify  the  resolution  of  an  image, measured in dots per inch.  The resolution
              affects some algorithms and it's recorded in DjVu and BMP files (TIFF  should  join
              someday).

       -e

       --erosion
              Sacrifice  image  quality  to gain about 5-10% in file size.  One erosion is almost
              invisible, but 10 erosions in a row spoil an image badly (and they won't  give  you
              50-100% of file size, alas).  Erosion bonus stacks with pattern matching.

              Erosion makes no sense when the output is not DjVu.

              This option is turned on by --lossy.

       -i

       --indirect

              Specifying  this  option  in multipage mode causes minidjvu to generate an indirect
              multipage document, consisting from a single index file, several  single-page  DjVu
              files  (one  per  each  image  passed to the encoder) and several shared dictionary
              files. Note that the index file is created under the name specified for the  output
              file  in  the  command  line,  while  for each page the original input file name is
              preserved, with the extension being changed to ".djvu".

              This mode is useful for placing a large document to a Web server,  or  if  you  are
              going  to  postprocess the generated files (e. g. by adding a color background). In
              the later case you may then want to convert your indirect document to DjVu bundled,
              using the djvmcvt utility, supplied with DjVuLibre.

       -l

       --lossy
              Turn on all lossy options. Is equivalent to --clean --erosion --match --smooth.

       -m

       --match
              Run  pattern  matching.  This is the main method of shrinking the file size, but it
              can also bring  trouble  with  substitution  errors.  Use  --aggression  option  to
              maintain balance between file size and error probability.

              This option is turned on by --lossy or --aggression.

       -n

       --no-prototypes
              Disable  prototype  searching. This makes lossless compression faster, but produced
              files become much bigger.

       -p

       --pages-per-dict
              Specify how many pages to compress in one pass. The default  is  10.  If  -p  0  is
              specified,  minidjvu  will  attempt to process all pages at once, but be aware that
              this can take a lot of memory, especially on large books.

       -r

       --report
              Print verbose messages about what's done on which page.  Works only with  multipage
              encoding.  Useful only to survive boredom while compressing a book.

       -s

       --smooth
              Flip  some  pixels  that  appear  to  be  noise. The gain in file size is about 5%.
              Visually the image is slightly improved, but it's hardly noticeable.

              Current filter is dumb and  only  removes  black  pixels  with  at  least  3  white
              neighbors (of 4). You probably won't notice the effects.

              This option is turned on by --lossy.

       -v

       --verbose
              Print  messages  about  various  stages  of the process.  It's not very useful, but
              interesting to examine.

       -X

       --Xtension
              Specifies an extension for shared dictionary files (without a leading period).  The
              default is "iff".

       -w

       --warnings
              Do  not  disable libtiff warnings. By default, TIFF warnings are suppressed.  Under
              Windows default TIFF warning handler creates a message box.  This  is  unacceptable
              in  a batch processing script, for instance.  So the minidjvu default behavior is a
              workaround for libtiff default behavior.

BUGS

       Multipage encoder does not work properly if pages have different resolution.