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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 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
          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
          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)



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