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.TH "TIFFDITHER" "1" "Jun 10, 2023" "4.5" "LibTIFF"
.SH NAME
tiffdither \- convert a greyscale TIFF image to bilevel using dithering
.SH SYNOPSIS
.sp
\fBtiffdither\fP [ \fIoptions\fP ] \fIinput.tif\fP \fIoutput.tif\fP
.SH DESCRIPTION
.sp
\fBtiffdither\fP converts a single channel 8\-bit greyscale image to a bilevel image
using Floyd\-Steinberg error propagation with thresholding.
.SH OPTIONS
.INDENT 0.0
.TP
.B \-c compress
Specify the compression to use for data written to the output file:
.TS
center;
|l|l|.
_
T{
Compression
T}	T{
Description
T}
_
T{
none
T}	T{
no compression
T}
_
T{
packbits
T}	T{
PackBits compression
T}
_
T{
lzw
T}	T{
Lempel\-Ziv & Welch compression
T}
_
T{
zip
T}	T{
Deflate compression
T}
_
T{
g3
T}	T{
CCITT Group 3 (T.4) compression
T}
_
T{
g4
T}	T{
for CCITT Group 4 (T.6) compression
T}
_
.TE
.sp
By default \fBtiffdither\fP
will compress data according to the value of the
\fBCompression\fP tag found in the source file.
.sp
The CCITT Group 3 and Group 4 compression algorithms can only
be used with bilevel data.
.sp
Group 3 compression can be specified together with several
T.4\-specific options:
\fB1d\fP for 1\-dimensional encoding,
\fB2d\fP for 2\-dimensional encoding, and
\fBfill\fP 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 \fB:\fP\-separated
list to the \fBg3\fP option; e.g. \fB\-c g3:2d:fill\fP
to get 2D\-encoded data with byte\-aligned EOL codes.
.sp
LZW compression can be specified together with a \fBpredictor\fP 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 \fB:\fP\-separated
list to the \fBlzw\fP option; e.g. \fB\-c lzw:2\fP for LZW
compression with horizontal differencing.
.UNINDENT
.INDENT 0.0
.TP
.B \-f
Specify the bit fill order to use in writing output data.
By default, \fBtiffdither\fP
will create a new file with the same fill order as the original.
Specifying
\fB\-f lsb2msb\fP will force data to be written with the
\fBFillOrder\fP tag set to \fBLSB2MSB\fP, while
\fB\-f msb2lsb\fP will force data to be written with the
\fBFillOrder\fP tag set to \fBMSB2LSB\fP\&.
.UNINDENT
.INDENT 0.0
.TP
.B \-r
Make each strip have no more than the given number of rows.
.UNINDENT
.INDENT 0.0
.TP
.B \-t
Set the threshold value for dithering.
By default the threshold value is 128.
.UNINDENT
.SH NOTES
.sp
The dither algorithm is taken from the \fBtiffmedian\fP
program (written by Paul Heckbert).
.SH SEE ALSO
.sp
\fI\%pal2rgb\fP (1),
\fI\%fax2tiff\fP (1),
\fI\%tiffinfo\fP (1),
\fI\%tiffcp\fP (1),
\fI\%tiff2bw\fP (3tiff)
.SH AUTHOR
LibTIFF contributors
.SH COPYRIGHT
1988-2022, LibTIFF contributors
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