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ddjvu

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 (PGM) 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. The resulting file uses the best available lossless compression model. 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 the best available lossless compression model. 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.

-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.

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 compression in TIFF and PDF files. Without this option, TIFF or PDF output files always use lossless compression or no compression. Argument factor specifies a JPEG 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.

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 -size=100x100 myfile.djvu -

produces a thumbnail for the first page of a document and outputs it as a PPM file on the standard output.

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.

SEE ALSO

djvu(1), djview(1), pnm(5), pbm(5), pgm(5), ppm(5), cjpeg(1), tiffsplit(1), tiffcp(1)