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tiffdither - convert a greyscale image
to bilevel using dithering
tiffdither [ options ] input.tif output.tif
tiffdither converts a single channel 8-bit greyscale image
to a bilevel image using Floyd-Steinberg error propagation with threholding.
- -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 .
- -t
- Set the threshold value for dithering. By default the threshold
value is 128.
The dither algorithm is taken from the tiffmedian(1)
program (written by Paul Heckbert).
pal2rgb(1)
, fax2tiff(1)
,
tiffinfo(1)
, tiffcp(1)
, tiff2bw(1)
, libtiff(3)
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