177 lines
5.4 KiB
ReStructuredText
177 lines
5.4 KiB
ReStructuredText
.. RST source for jbig2(1) man page. Convert with:
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.. rst2man.py jbig2.rst > jbig2.1
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.. rst2man.py comes from the SBo development/docutils package.
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.. |version| replace:: 0.28
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.. |date| date::
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=====
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jbig2
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=====
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-----------------------------------
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convert image files to JBIG2 format
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-----------------------------------
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:Manual section: 1
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:Manual group: SlackBuilds.org
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:Date: |date|
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:Version: |version|
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SYNOPSIS
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========
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**jbig2** [*-options*] *imagefile* > *output.jb2*
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DESCRIPTION
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===========
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JBIG2 is an image compression standard from the same people who brought
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you the JPEG format. It compresses 1bpp (black and white) images only.
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jbig2enc is a library that encodes JBIG2 images.
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**jbig2** is a command-line tool that uses the jbig2enc library to convert an
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image to the JBIG2 format. *imagefile* can be in any format readable by
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leptonica (png, jpeg, tiff, gif, webp, jp2, bmp, pnm, spix). The image
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is converted to 1bbp (monochrome) before processing.
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Without the *-p*, *--pdf* option, the converted image is written to
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standard output. This should be redirected to a file, normally with
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the *.jb2* extension. If stdout isn't redirected to a file (or a pipe),
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the JBIG2 data will be written to the terminal, which may get confused.
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There is no way to have **jbig2** read an image file on standard input. This
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is by design, as it needs to seek within the file.
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All options must appear before the filename. With the generic encoder
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(no *-s* option), anything after the filename is silently ignored. The
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symbol encoder (*-s*) can handle multiple images (which end up as pages
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in the JBIG2 file).
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The *-r*, *--refine* option mentioned in the documentation and in
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the *--help* output of **jbig2** is *disabled* in this version of
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**jbig2**.
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OPTIONS
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=======
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.. some of these are from the HTML file, some from --help.
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-b *basename*
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Output file root name when using symbol coding in PDF mode (*-s*
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and *-p*). Default is **output**.
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-d, --duplicate-line-removal
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When encoding generic regions each scan line can be tagged to indicate
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that it's the same as the last scanline - and encoding that scanline
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is skipped. This drastically reduces the encoding time (by a factor
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of about 2 on some images) although it doesn't typically save any
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bytes. This is an option because some versions of jbig2dec (an open
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source decoding library) cannot handle this.
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-p, --pdf
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The PDF spec includes support for JBIG2 (Syntax->Filters->JBIG2Decode in
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the PDF references for versions 1.4 and above). However, PDF requires
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a slightly different format for JBIG2 streams: no file/page headers or
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trailers and all pages are numbered 1. In symbol mode the output is to
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a series of files: symboltable and page-n (numbered from 0). By default
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these are named **output.sym** and **output.0000**, **output.0001**,
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etc. Use *-b* to change the base filename.
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-s, --symbol-mode
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Use symbol encoding. Turn on for scanned text pages.
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-t *threshold*
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Sets the fraction of pixels which have to match in order for
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two symbols to be classed the same. This isn't strictly true, as there are
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other tests as well, but increasing this will generally increase the number
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of symbol classes. Default is 0.85.
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-T *threshold*
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Sets the black threshold (0-255). Any gray value darker than
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this is considered black. Anything lighter is considered white.
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Default is 188.
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-O *outfile*
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Dump a PNG of the 1 bpp image before encoding. Can be used to
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test loss.
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-2, -4
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Upscale either two or four times before converting to black and
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white.
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-S
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Segment an image into text and non-text regions. This isn't perfect, but
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running text through the symbol compressor is terrible so it's worth doing
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if your input has images in it (like a magazine page).
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--image-output
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Set filename to which the parts which were removed by -S are written.
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Default is PNG format.
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-j, --jpeg-output
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Write images from -S as JPEG instead of PNG.
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-a, --auto-thresh
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Use automatic thresholding in symbol encoder.
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--no-hash
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Disables use of hash function for automatic thresholding.
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-v
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Be verbose.
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-V, --version
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Display version number and exit.
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-h, --help
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Display help and exit.
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EXIT STATUS
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===========
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**jbig2** exits with 0 (success) status if the conversion completed
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OK, and non-zero status if anything went wrong. If standard output was
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redirected to a file, the file will be empty or invalid when non-zero
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status is returned. Diagnostic messages are printed to standard error.
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COPYRIGHT
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=========
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See the file /usr/doc/jbig2enc-|version|/COPYING for license information.
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This software is a description of processes which may be patented.
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Use of this software may require patent licenses in some countries.
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You are directed to annex I of the JBIG2 specification for information.
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Some information could be found at:
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http://www.jpeg.org/jbig/index.html
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http://www.cl.cam.ac.uk/~mgk25/jbigkit/patents/
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http://www.jpeg.org/public/fcd14492.pdf
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http://itscj.ipsj.or.jp/sc29/open/29view/29n55161.doc
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AUTHORS
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=======
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jbig2 and jbig2enc were written by:
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Adam Langley <agl@imperialviolet.org>.
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This man page written for the SlackBuilds.org project
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by B. Watson, and is licensed under the WTFPL.
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SEE ALSO
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========
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**pdf.py(1)**, **jbig2dec(1)**
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Full documentation for jbig2 and jbig2enc:
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/usr/doc/jbig2enc-|version|/jbig2enc.html
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The JBIG2 specification was formerly located at:
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http://www.jpeg.org/public/fcd14492.pdf
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A copy can be found here:
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http://www.hlevkin.com/Standards/fcd14492.pdf
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