TIFFDITHER(1) User Commands TIFFDITHER(1)

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).

SEE ALSO

pal2rgb(1), fax2tiff(1), tiffinfo(1), tiffcp(1), tiff2bw(1),
libtiff(3TIFF)

Libtiff library home page: http://www.simplesystems.org/libtiff/

libtiff September 20, 2005 TIFFDITHER(1)