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PNGNQ(1)			 User Manuals			      PNGNQ(1)

NAME
       pngnq - quantize	png images

SYNOPSIS
       pngnq  [-vfhV][-s  sample_factor	 ][-Q dither ][-g gamma	][-e extension
       ][-d dir	][-n colors ][ inputfiles ]

DESCRIPTION
       pngnq Quantizes a 32-bit	RGBA PNG image to an 8 bit  RGBA  palette  PNG
       using  the  neuquant  algorithm.	The output file	name is	the input file
       name extended with "-nq8.png" or	a specified extension.

OPTIONS
       -v     Verbose mode. Prints status messages.

       -f     Force ovewriting of files.

       -s sample factor
	      Sample factor. The neuquant algorithm samples pixels stepping by
	      this value.  The default value of	3 gives	good  results.	Higher
	      values  sample  less of the image	pixels and thus	are faster but
	      less accurate. A factor of 1 samples every image pixel.

       -n colors
	      Specifies	the number of colors to	quantize to. Defaults  to  256
	      which is the maximum.  The minimum here is 2.

       -Q dither
	      Choose  a	 dithering  method: n =	no dither (default), f = Floyd
	      Steinberg	dithering.

       -g gamma
	      Set the image gamma correction. If not  present,	uses  the  png
	      file's gamma or defaults to 1.0.

       -e extension
	      Specifies	 the  new  filename extension. Defaults	to "-nq8.png".
	      Pngnq drops .png from the	original filenames. If you set the ar-
	      gument of	the -e option to .png and choose the -f	option the in-
	      put file will be overwritten.

       -d dir Tells pngnq to put output	files in a directory  other  than  the
	      one the input files are in.

       input files
	      The png files to be processed. Defaults to standard input	if not
	      specified.   If  standard	input is being processed the output is
	      sent to standard output.

       -h     Print program help.

       -V     Print version number and library versions.

BUGS
       Does not	deal correctly	with  greyscale	 alpha	images	with  low  bit
       depths, but these wont benefit from quantizing.

AUTHOR
       Stuart Coyle <stuart.coyle@gmail.com>

SEE ALSO
       png(5)

Linux				   MAY 2009			      PNGNQ(1)

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