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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 overwriting 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 val-
	      ues 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 argument
	      of the -e option to .png and choose the -f option the input 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)