PNGQUANT(1) General Commands Manual PNGQUANT(1)NAME
pngquant - PNG image optimising utility
SYNOPSIS
pngquant [ options ] <ncolors> [pngfile [pngfile ...]]
pngquant [ options ] -map mapfile [pngfile [pngfile ...]]
Note that it's required to specify the number of colors (<ncolors>) or the mapfile. Arguments in square brackets are optional.
DESCRIPTION
This manual page documents briefly the pngquant command.
pngquant quantizes one or more 32-bit RGBA PNGs to 8-bit (or smaller) RGBA-palette PNGs using either ordered dithering or Floyd-Steinberg
diffusion dithering (default). The output filename is the same as the input name except that it ends in -fs8.png or -or8.png (unless the
input is stdin, in which case the quantized image will go to stdout). The default behavior if the output file exists is to skip the con-
version; use -force to overwrite.
OPTIONS -force Overwrite existing output files.
-ordened, -nofloyd, -nofs
Use ordered dithering.
-verbose, -noquiet
Print status messages.
NOTE: the -map option is NOT YET SUPPORTED.
EXAMPLE
Creating a new image with the number of colors reduced to 64:
pngquant 64 image.png
The resulting image will have 64 colors and will be saved as image-fs8.png.
AUTHOR
pngquant was written by Greg Roelofs <newt@pobox.com>.
This manual page was written by Nelson A. de Oliveira <naoliv@debian.org>, for the Debian project (but may be used by others).
Thu, 07 Dec 2006 00:33:40 -0200PNGQUANT(1)
Check Out this Related Man Page
ppmquant(1) General Commands Manual ppmquant(1)NAME
ppmquant - quantize the colors in a portable pixmap down to a specified number
SYNOPSIS
ppmquant [-floyd|-fs] ncolors [ppmfile]
ppmquant [-floyd|-fs] [-nofloyd|-nofs] -mapfile mapfile [ppmfile]
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
pnmquant is a newer, more general program that is backward compatible with ppmquant. ppmquant may be faster, though.
Reads a PPM image as input. Chooses ncolors colors to best represent the image, maps the existing colors to the new ones, and writes a PPM
image as output.
The quantization method is Heckbert's "median cut".
Alternately, you can skip the color-choosing step by specifying your own set of colors with the -mapfile option. The mapfile is just a ppm
file; it can be any shape, all that matters is the colors in it. For instance, to quantize down to the 8-color IBM TTL color set, you
might use:
P3
8 1
255
0 0 0
255 0 0
0 255 0
0 0 255
255 255 0
255 0 255
0 255 255
255 255 255
If you want to quantize one image to use the colors in another one, just use the second one as the mapfile. You don't have to reduce it
down to only one pixel of each color, just use it as is.
If you use a mapfile, the output image has the same maxval as the mapfile. Otherwise, the output maxval is the same as the input maxval,
or less in some cases where the quantization process reduces the necessary resolution.
The -floyd/-fs option enables a Floyd-Steinberg error diffusion step. Floyd-Steinberg gives vastly better results on images where the
unmodified quantization has banding or other artifacts, especially when going to a small number of colors such as the above IBM set. How-
ever, it does take substantially more CPU time, so the default is off.
-nofloyd/-nofs means not to use the Floyd-Steinberg error diffusion. This is the default.
REFERENCES
"Color Image Quantization for Frame Buffer Display" by Paul Heckbert, SIGGRAPH '82 Proceedings, page 297.
SEE ALSO pnmquant(1), ppmquantall(1), pnmdepth(1), ppmdither(1), ppm(5)AUTHOR
Copyright (C) 1989, 1991 by Jef Poskanzer.
12 January 1991 ppmquant(1)