Manual: pnmquant

Pnmquant User Manual(1)				   General Commands Manual			     Pnmquant User Manual(1)

NAME
       pnmquant - quantize the colors in a Netpbm image to a smaller set

SYNOPSIS
       pnmquant	 [-center|-meancolor|-meanpixel]  [-floyd|-fs] [-nofloyd|-nofs] [-spreadbrightness|-spreadluminosity] {[-no‐
       random]|[-randomseed=n]} ncolors [pnmfile]

       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 equals signs between an option name and its value.

DESCRIPTION
       This program is part of Netpbm(1).

       pnmquant reads a PNM image as input.  It chooses ncolors colors to best represent the image, maps the existing colors
       to the new ones, and writes a PNM image as output.

       This  program is simply a combination of pnmcolormap and pnmremap, where the colors of the input are remapped using a
       color map which is generated from the colors in that same input.	 The options have the same meaning as in those	pro‐
       grams.  See their documentation to understand pnmquant.

       You may actually get fewer than ncolors colors in the output because
	 the method pnmcolormap uses to choose the best set of colors for the
	 image is not the same as the method pnmremap uses to determine the
	 best color from the set to represent an individual color.  For example,
	 pnmcolormap may include salmon in the color map as the best
	 representative of a pink pixel in the input and include coral in the color
	 map as the best representative of an actual coral pixel in the input.	But
	 pnmremap is free to use any color in the color map to represent that
	 pink pixel and would find coral is a closer match for pink than salmon and
	 therefore use coral for pink.	pnmremap might not use salmon
	 for any pixel.

       This waste of a slot in the color map is a consequence of the approximate
	 method pnmcolormap uses in order to compute the color map with a
	 practical amount of computation.

   Running pnmcolormap and pnmremap Separately
       It  is much faster to call pnmcolormap and pnmremap directly than to run pnmquant.  You save the overhead of the Perl
       interpreter and creating two extra processes.  pnmquant is just a convenience.

       Here is an example of the relationship between the programs:

       This:

	   $ pnmquant 256 myimage.pnm >/tmp/colormap.pnm >myimage256.pnm

       does essentially this:

	   $ pnmcolormap 256 myimage.pnm >/tmp/colormap.pnm
	   $ pnmremap -mapfile=/tmp/colormap.pnm myimage.pnm >myimage256.pnm

OPTIONS
       In addition to the options common to all programs based on libnetpbm (most notably -quiet, see  Common Options ), pn‐
       mquant recognizes the following command line options:

   Options Passed to pnmcolormap
       These options control the selection of the palette.  They are options to pnmcolormap(1).

       -center

       -meancolor

       -meanpixel

       -spreadbrightness

       -spreadluminosity

   Options Passed to pnmremap
       These options control which color from the palette the program uses to
	 replace a pixel of a certain color from the input.  They are options to pnmremap(1).

       -floyd

       -fs

       -nofloyd

       -nofs

       -norandom

       -randomseed

       -norandom

HISTORY
       pnmquant did not exist before Netpbm 9.21 (January 2001).  Before that, ppmquant did the same thing, but only on	 PPM
       images.	ppmquant continues to exist, but is only a front end (for name compatibility) to pnmquant.

       -version did not exist before Netpbm 10.75 (June 2016).

       -norandom did not exist before Netpbm 10.82 (March 2018).

SEE ALSO
       pnmcolormap(1), pnmremap(1), pnmquantall(1), pamdepth(1), ppmdither(1), ppmquant(1), pnm(1)

DOCUMENT SOURCE
       This manual page was generated by the Netpbm tool 'makeman' from HTML source.  The master documentation is at

	      http://netpbm.sourceforge.net/doc/pnmquant.html

netpbm documentation				      09 February 2019				     Pnmquant User Manual(1)