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 .
- -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.remotesensing.org/libtiff/