phpman > man > ppmdither(1)

Che Dong

Reduce the number of colors in an image by applying dithering.

Read a PPM image, apply dithering, and save it to a file
ppmdither {{path/to/image.ppm}} > {{path/to/file.ppm}}
Specify the desired number of shades for each primary color
ppmdither {{-r|-red}} {{2}} {{-g|-green}} {{3}} {{-b|-blue}} {{2}} {{path/to/image.ppm}} > {{path/to/file.ppm}}
Specify the dimensions of the dithering matrix
ppmdither {{-d|-dim}} {{2}} {{path/to/image.ppm}} > {{path/to/file.ppm}}

ppmdither(1)                           General Commands Manual                          ppmdither(1)



NAME
       ppmdither - ordered dither for color images

SYNOPSIS
       ppmdither [-dim power] [-red shades] [-green shades] [-blue shades] [ppmfile]

DESCRIPTION
       Reads  a portable pixmap as input, and applies dithering to it to reduce the number of colors
       used down to the specified number of shades for each primary.  The default number  of  shades
       is  red=5,  green=9, blue=5, for a total of 225 colors.  To convert the image to a binary rgb
       format suitable for color printers, use -red 2 -green 2 -blue 2.


OPTIONS
       -dim power    The size of the dithering matrix.  The dithering matrix is a square  whose  di‐
                     mension is a power of 2.  power is that power of 2.  The default is 4, for a 16
                     by 16 matrix.

       -red shades   The number of red shades to be used, including black; minimum of 2.

       -green shades The number of green shades to be used, including black; minimum of 2.

       -blue shades  The number of blue shades to be used, including black; minimum of 2.

SEE ALSO
       pnmdepth(1), ppmquant(1), ppm(5)

AUTHOR
       Copyright (C) 1991 by Christos Zoulas.



                                            14 July 1991                                ppmdither(1)

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