tiffdither (1)

Leading comments

$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 a...

(The comments found at the beginning of the groff file "man1/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 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 .

-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.

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: www.simplesystems.org/libtiff