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.