TIFFDITHER(1) General Commands Manual TIFFDITHER(1) 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 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 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 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- tal 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/ libtiff September 20, 2005 TIFFDITHER(1)
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