# TIFFDITHER

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
NOTES
SEE ALSO

## 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 threholding.

## 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 .

| -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(3)