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TIFFDITHER
TIFFDITHER
NAME
SYNOPSIS
DESCRIPTION
OPTIONS
NOTES
SEE ALSO
NAME
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tiffdither − convert a greyscale image to bilevel
using dithering
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SYNOPSIS
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tiffdither [ options ] input.tif
output.tif
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DESCRIPTION
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tiffdither converts a single channel 8-bit
greyscale image to a bilevel image using Floyd-Steinberg
error propagation with thresholding.
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OPTIONS
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−c
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Specify the compression to use for data written to the
output file: none for no compression, packbits
for PackBits compression, lzw for Lempel-Ziv &
Welch compression, zip for Deflate compression,
g3 for CCITT Group 3 (T.4) compression, and g4
for CCITT Group 4 (T.6) compression. By default
tiffdither will compress data according to the value
of the Compression tag found in the source file.
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The CCITT Group 3 and Group 4 compression
algorithms can only be used with bilevel data.
Group 3 compression can be specified together with
several T.4-specific options: 1d for 1-dimensional
encoding, 2d for 2-dimensional encoding, and
fill to force each encoded scanline to be zero-filled
so that the terminating EOL code lies on a byte boundary.
Group 3-specific options are specified by appending a
‘‘:’’-separated list to the
‘‘g3’’ option; e.g. −c
g3:2d:fill to get 2D-encoded data with byte-aligned EOL
codes.
LZW compression can be specified together
with a predictor value. A predictor value of 2 causes
each scanline of the output image to undergo horizontal
differencing before it is encoded; a value of 1 forces each
scanline to be encoded without differencing. LZW-specific
options are specified by appending a
‘‘:’’-separated list to the
‘‘lzw’’ option; e.g. −c
lzw:2 for LZW compression with horizontal
differencing.
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−f
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Specify the bit fill order to use in writing output
data. By default, tiffdither will create a new file
with the same fill order as the original. Specifying
−f lsb2msb will force data to be written with
the FillOrder tag set to LSB2MSB ,
while −f msb2lsb will force data to be written
with the Fill- Order tag set to MSB2LSB
.
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−r
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Make each strip have no more than the given number of rows.
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−t
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Set the threshold value for dithering. By default the
threshold value is 128.
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NOTES
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The dither algorithm is taken from the
tiffmedian(1) program (written by Paul Heckbert).
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SEE ALSO
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pal2rgb(1), fax2tiff(1),
tiffinfo(1), tiffcp(1), tiff2bw(1),
libtiff(3TIFF)
Libtiff library home page:
http://www.simplesystems.org/libtiff/
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