Ubuntu Manpage: ddjvu - Command line DjVu decoder.

Provided by: djvulibre-bin_3.5.28-2ubuntu0.24.04.1_amd64

NAME

       ddjvu - Command line DjVu decoder.

SYNOPSIS

       ddjvu -format=fmt [options] [djvufile] [outputfile]

DESCRIPTION

       Decode the DjVu file djvufile, produces the image file outputfile.

       The DjVu data is read from the standard input when argument djvufile is not specified or when it is equal
       to  a single dash.  Similarly, the output data is written to the standard output when argument outputfile
       is not specified or equal to a single dash.  However a valid output file name  is  always  required  when
       producing a TIFF or PDF file.

MAIN OPTIONS

-format=fmt
Specify the output file formats. The recognized file formats are pbm, pgm, ppm, pnm, rle, tiff,
and pdf.

* Formats pbm, pgm, and ppm respectively produce a Portable Bitmap (PBM), Portable Graymap (PGM),
or Portable Pixmap (PPM) file. Format pnm produces a PBM, PGM, or PPM output file according to
the color content of the output image.

* Format rle produces a compact run length encoded bitonal file that is understood by the
DjVuLibre commands cjb2 and csepdjvu.

* Format tiff produces a Tagged Image Format (TIFF) file using lossless compression. Enabling
lossy JPEG compression (see option -quality below) often produces much smaller files. Commands
tiffcp(1) and tiffsplit(1) are useful for manipulating the resulting TIFF files.

* Format pdf produces a Portable Document Format (PDF) file. Each page in the resulting file is
represented by an image at the specified resolution, using lossless compression. Enabling
lossy JPEG compression (see option -quality below) often produces much smaller files. An
alternate way to produce PDF file consists in first using djvups(1) and convert the resulting
PostScript file to PDF. Which method gives better results depends on the contents of the DJVU
file and on the capabilities of the PS to PDF converter.

When option -format is not specified, the extension of argument outputfile has no influence on the
default output format. Instead the program behavior is modified to ensure backward compatibility
with previous versions of ddjvu. We recommend to always specify the output format using this
option.

-page=pagespec
Specify which pages should be decoded. When this option is not specified, all pages of the
documents are decoded and concatenated into the output file. The page specification pagespec
contains one or more comma-separated page ranges. A page range is either a page number, or two
page numbers separated by a dash. For instance, specification 1-10 outputs pages 1 to 10, and
specification 1,3,99999-4 outputs pages 1 and 3, followed by all the document pages in reverse
order up to page 4.

-eachpage
When this option is specified, program ddjvu generates one separate file per page named by
replacing the %d specification in outputfilename by the page number in a manner simular to the
printf(3) function.

-mode=mod
Selects which layers of the DjVu image should be rendered. Valid rendering modes are color,
black, mask, foreground, and background.

* Rendering mode color is the default mode. When the DjVu file is bitonal, bitonal or gray-level
output is produced depending on the subsampling factor. Otherwise a color image is produced.

* Rendering mode black is useful to extract a meaningful black and white image. bitonal or gray-
level output is produced depending on the subsampling factor.

* Rendering modes mask, foreground, and background select specific layers of a DjVu image. These
modes can fail if the DjVu image does not contain the selected layer.

-skip Instead of aborting when encountering a corrupted page, this option causes ddjvu to simply skip
the corrupted page and continue with the next. This is useful for processing certain damaged
files.

RESOLUTION OPTIONS

The following options control the resolution of the output image. The default resolution is the native
resolution of the DjVu file, equivalent to selecting -1.

-n Specify an integer sub-sampling factor. The dimensions of the full output image will be n times
smaller than the DjVu image size. The legal values for argument n range from 1 to 12. Option -1,
for instance, produces an output image whose resolution is equal to the resolution of the input
DjVu image file.

-subsample=n
This is equivalent to option -n.

-scale=mag
Specify a magnification factor relative to the resolution stored in the DjVu image. Specifying
magnification of 100 produces an image suitable for displaying on a 100 dpi device such as a
computer screen. The magnification factor mag can also be interpreted as the resolution of the
output image expressed in dot per inch.

-size=wxh
Specify the size of the full output image. Rendering the full DjVu image would create an output
image whose width and height would not exceed w and h. To change the aspect ratio, you must also
use option -aspect=no.

-aspect=yesno
This option indicates whether the image aspect ratio should be preserved. The defaults is to
preserve the aspect ration. This option permits changes in the aspect ratio when used in
combination with option -size.

OTHER OPTIONS

-verbose
Display informational messages describing the structure of the DjVu image and the format of the
output file.

-segment=wxh+x+y
Specify an image segment to render. Program ddjvu conceptually renders the full page using the
specified resolution, and then extracts a sub-image of width w and height h, starting at position
(x,y) relative to the bottom left corner of the page. Both operations of course happen
simultaneously. Rendering a small sub-image is much faster than rendering the complete image.
The output file will always have size wxh when this option is specified.

-quality=factor
Enables lossy JPEG compression for TIFF and PDF files. This option only affects images that
cannot be encoded using the preferred TIFF/G4 compression. Argument factor is a quantization
factor ranging from 25 to 150. See command cjpeg(1) for more information on JPEG quantization
factors. Value 80 is a good starting point.

-quality=uncompressed
Completely disables compression in TIFF and PDF files. Although the resulting files are often
huge, this is sometimes useful for maximal compatibility with hastily written software.

-quality=deflate
Enables DEFLATE compression for TIFF files. Images that cannot be encoded using the preferred
TIFF/G4 compression will be encoded with DEFLATE compression if available. Otherwise the more
portable PACKBITS compression is used. Specifying this option is not necessary for PDF files
because this is the default behavior.

DEPRECATED OPTIONS

       Various  options  have  been maintained to ensure backward compatibility with previous versions of ddjvu.
       When option -format is not specified, the program only decodes the first page of  the  document  and  the
       default  resolution  becomes  -scale=100.   Options -size, -scale, -segment, and -page accept an argument
       separated by a space.  Options -foreground, -background, and -black  are  shorthands  for  the  -mode=mod
       option.  Please do not rely on these features.

EXAMPLES

       Command

          ddjvu -format=tiff myfile.djvu myfile.tif

       decodes all pages and produces a multipage TIFF file.

       Command

          ddjvu -format=ppm -page=1-10 -eachpage -size=100x100 myfile.djvu thumb%03d.ppm

       produces  100x100  thumbnails  for  the  first ten page of a document and outputs them as PPM files named
       thumb001.ppm to thumb010.ppm.

CREDITS

       The new version of this program was written by Léon Bottou <leonb@users.sourceforge.net>.

       This program includes code derived from program tiff2pdf, written by Ross Finlayson and released under  a
       BSD license.