tiffdither - convert a greyscale TIFF 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
thresholding.
- -c compress
- Specify the compression to use for data written to the output file:
Compression |
Description |
none |
no compression |
packbits |
PackBits compression |
lzw |
Lempel-Ziv & Welch
compression |
zip |
Deflate compression |
g3 |
CCITT Group 3 (T.4)
compression |
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.
The dither algorithm is taken from the tiffmedian program
(written by Paul Heckbert).
pal2rgb (1), fax2tiff (1), tiffinfo (1),
tiffcp (1), tiff2bw (3tiff)
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