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)