$Id: tiffdither.1,v 1.6 2016-09-25 20:05:52 bfriesen Exp $

Copyright (c) 1990-1997 Sam Leffler
Copyright (c) 1991-1997 Silicon Graphics, Inc.

Permission to use, copy, modify, distribute, and sell this software and
its documentation for any purpose is hereby granted without fee, provided
that (i) the above copyright notices and this permission notice appear in
all copies of the software and related documentation, and (ii) the names of
Sam Leffler and Silicon Graphics may not be used in any advertising or
publicity relating to the software without the specific, prior written
permission of Sam Leffler and Silicon Graphics.

THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND,
EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
OF THIS SOFTWARE.

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 thresholding.

-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 Fill\%Order tag set to LSB2MSB , while "-f msb2lsb" will force data to be written with the Fill\%Order 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 (1) program (written by Paul Heckbert). pal2rgb (1), fax2tiff (1), tiffinfo (1), tiffcp (1), tiff2bw (1), libtiff (3TIFF)

Libtiff library home page: http://www.simplesystems.org/libtiff/