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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 compres-
sion, 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
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 differ-
encing before it is encoded; a value of 1 forces each scanline to be encoded with-
out differencing. LZW-specific options are specified by appending a ``:''-sepa-
rated list to the ``lzw'' option; e.g. -c lzw:2 for LZW compression with horizon-
-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)
October 15, 1995 TIFFDITHER(1)
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