TIFFDITHER(1)TIFFDITHER(1)NAMEtiffdither - convert a greyscale image to bilevel using
dithering
SYNOPSIStiffdither [ options ] input.tif output.tif
DESCRIPTIONtiffdither converts a single channel 8-bit greyscale image
to a bilevel image using Floyd-Steinberg error propagation
with threholding.
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 algo
rithms 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 bound
ary. 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 hori
zontal 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 Fil
lOrder tag set to MSB2LSB .
-t Set the threshold value for dithering. By default
the threshold value is 128.
NOTES
The dither algorithm is taken from the tiffmedian(1) pro
gram (written by Paul Heckbert).
SEE ALSOpal2rgb(1), fax2tiff(1), tiffinfo(1), tiffcp(1),
tiff2bw(1), libtiff(3)
October 15, 1995 TIFFDITHER(1)
