<meta content="groff -Thtml, see www.gnu.org" name="generator">

<meta content="text/css" name="Content-Style">

<title>TIFFDITHER</title>

TIFFDITHER

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

NOTES

SEE ALSO

NAME

       cols="2" cellspacing="0" cellpadding="0">

tiffdither − convert a greyscale image to bilevel

using dithering

SYNOPSIS

       cols="2" cellspacing="0" cellpadding="0">

tiffdither [ options ] input.tif

output.tif

DESCRIPTION

       cols="2" cellspacing="0" cellpadding="0">

tiffdither converts a single channel 8-bit

greyscale image to a bilevel image using Floyd-Steinberg

error propagation with thresholding.

OPTIONS

       cols="5" cellspacing="0" cellpadding="0">

−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.

       cols="2" cellspacing="0" cellpadding="0">

The <small>CCITT</small> 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.

<small>LZW</small> 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 <small>LZW</small> compression with horizontal

differencing.

       cols="5" cellspacing="0" cellpadding="0">

−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 <small>LSB2MSB ,</small>

while −f msb2lsb will force data to be written

with the Fill- Order tag set to <small>MSB2LSB</small>

.

−t

Set the threshold value for dithering. By default the

threshold value is 128.

NOTES

       cols="2" cellspacing="0" cellpadding="0">

The dither algorithm is taken from the

tiffmedian(1) program (written by Paul Heckbert).

SEE ALSO

       cols="2" cellspacing="0" cellpadding="0">

pal2rgb(1), fax2tiff(1),

tiffinfo(1), tiffcp(1), tiff2bw(1),

libtiff(3TIFF)

Libtiff library home page:

http://www.remotesensing.org/libtiff/