126 lines
3.7 KiB
Groff
126 lines
3.7 KiB
Groff
.\" $Id: tiffdither.1,v 1.2 2005-09-20 10:29:15 dron Exp $
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.\"
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.\" Copyright (c) 1990-1997 Sam Leffler
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.\" Copyright (c) 1991-1997 Silicon Graphics, Inc.
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.\"
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.\" Permission to use, copy, modify, distribute, and sell this software and
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.\" its documentation for any purpose is hereby granted without fee, provided
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.\" that (i) the above copyright notices and this permission notice appear in
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.\" all copies of the software and related documentation, and (ii) the names of
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.\" Sam Leffler and Silicon Graphics may not be used in any advertising or
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.\" publicity relating to the software without the specific, prior written
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.\" permission of Sam Leffler and Silicon Graphics.
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.\"
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.\" THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND,
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.\" EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
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.\" WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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.\"
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.\" IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
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.\" ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
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.\" OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
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.\" WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
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.\" LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
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.\" OF THIS SOFTWARE.
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.\"
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.if n .po 0
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.TH TIFFDITHER 1 "September 20, 2005" "tiffdither"
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.SH NAME
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tiffdither \- convert a greyscale image to bilevel using dithering
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.SH SYNOPSIS
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.B tiffdither
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[
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.I options
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]
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.I input.tif
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.I output.tif
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.SH DESCRIPTION
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.I tiffdither
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converts a single channel 8-bit greyscale image to a bilevel image
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using Floyd-Steinberg error propagation with thresholding.
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.SH OPTIONS
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.TP
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.B \-c
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Specify the compression to use for data written to the output file:
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.B none
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for no compression,
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.B packbits
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for PackBits compression,
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.B lzw
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for Lempel-Ziv & Welch compression,
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.B zip
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for Deflate compression,
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.B g3
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for CCITT Group 3 (T.4) compression,
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and
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.B g4
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for CCITT Group 4 (T.6) compression.
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By default
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.I tiffdither
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will compress data according to the value of the
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.I Compression
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tag found in the source file.
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.IP
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The
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.SM CCITT
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Group 3 and Group 4 compression algorithms can only
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be used with bilevel data.
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.IP
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Group 3 compression can be specified together with several
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T.4-specific options:
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.B 1d
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for 1-dimensional encoding,
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.B 2d
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for 2-dimensional encoding,
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and
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.B fill
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to force each encoded scanline to be zero-filled so that the
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terminating EOL code lies on a byte boundary.
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Group 3-specific options are specified by appending a ``:''-separated
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list to the ``g3'' option; e.g.
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.B "\-c g3:2d:fill"
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to get 2D-encoded data with byte-aligned EOL codes.
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.IP
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.SM LZW
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compression can be specified together with a
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.I predictor
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value.
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A predictor value of 2 causes
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each scanline of the output image to undergo horizontal
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differencing before it is encoded; a value
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of 1 forces each scanline to be encoded without differencing.
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LZW-specific options are specified by appending a ``:''-separated
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list to the ``lzw'' option; e.g.
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.B "\-c lzw:2"
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for
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.SM LZW
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compression with horizontal differencing.
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.TP
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.B \-f
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Specify the bit fill order to use in writing output data.
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By default,
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.I tiffdither
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will create a new file with the same fill order as the original.
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Specifying
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.B "\-f lsb2msb"
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will force data to be written with the FillOrder tag set to
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.SM LSB2MSB ,
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while
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.B "\-f msb2lsb"
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will force data to be written with the FillOrder tag set to
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.SM MSB2LSB .
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.TP
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.B \-t
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Set the threshold value for dithering.
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By default the threshold value is 128.
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.SH NOTES
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The dither algorithm is taken from the
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.IR tiffmedian (1)
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program (written by Paul Heckbert).
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.SH "SEE ALSO"
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.IR pal2rgb (1),
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.IR fax2tiff (1),
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.IR tiffinfo (1),
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.IR tiffcp (1),
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.IR tiff2bw (1),
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.IR libtiff (3)
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