Tribblix: manual page: ddjvu.1

DDJVU(1) DjVuLibre-3.5 DDJVU(1)

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 L'eon Bottou
<leonb@users.sourceforge.net>.

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