This is the command tiffdither that can be run in the OnWorks free hosting provider using one of our multiple free online workstations such as Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator
PROGRAM:
NAME
tiffdither - convert a greyscale image to bilevel using dithering
SYNOPSIS
tiffdither [ options ] input.tif output.tif
DESCRIPTION
tiffdither converts a single channel 8-bit greyscale image to a bilevel image using Floyd-
Steinberg error propagation with thresholding.
OPTIONS
-c 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.
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.
-f 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 FillOrder tag set to MSB2LSB .
-r Make each strip have no more than the given number of rows.
-t Set the threshold value for dithering. By default the threshold value is 128.
NOTES
The dither algorithm is taken from the tiffmedian(1) program (written by Paul Heckbert).
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