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] {[-norandom]|[-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 gener-
ated from the colors in that same input. The options have the same
meaning as in those programs. 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 exam-
ple,
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 approxi-
mate
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 ⟨index.html#commonoptions⟩ ), pnmquant 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 contin-
ues to exist, but is only a front end (for name compatibility) to pn-
mquant.
-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), ppmquantall(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)
Generated by dwww version 1.15 on Sat Jun 29 02:16:25 CEST 2024.