Ppmdither User Manual(0) | Ppmdither User Manual(0) |

# NAME

ppmdither - ordered dither for color images

# SYNOPSIS

**ppmdither**

[**-dim**=*power*]

[**-red**=*n*]

[**-green**=*n*]

[**-blue**=*n*]

[*netpbmfile*]

All options can be abbreviated to their shortest unique prefix. You may use two hyphens instead of one to designate an option. You may use either white space or an equals sign between an option name and its value.

# DESCRIPTION

This program is part of Netpbm(1)

**ppmdither** reads a Netpbm image as input, and applies
dithering to it to reduce the number of colors used down to the specified
number of shades for each primary. It produces a PPM image as output.

The default number of shades is 5 red, 9 green, and 5 blue, for a
total of 225 colors. To convert the image to a binary rgb format suitable
for primitive color printers, use **-red=2 -green=2 -blue=2**.

You can do another kind of dither -- Floyd-Steinberg -- with
**pnmquant** or **pnmremap**.

# OPTIONS

**-dim***power*-

The size of the dithering matrix. The dithering matrix is a square whose dimension is a power of 2.*power*is that power of 2. The default is 4, for a 16 by 16 matrix. **-red**=*n*- The number of red shades to be used, including black; minimum of 2.
Default is 5.

**-green***n*- The number of green shades to be used, including black; minimum of 2.
Default is 9.

**-blue***n*- The number of blue shades to be used, including black; minimum of 2.
Default is 5.

# SEE ALSO

pamditherbw(1) , pamdepth(1) , pnmquant(1) , pnmremap(1) , ppm(5)

# AUTHOR

Copyright (C) 1991 by Christos Zoulas.

16 December 2009 | netpbm documentation |