pngnq - quantize png images
pngnq [-vfhV][-s sample_factor ][-Q dither
][-g gamma ][-e extension ][-d dir
][-n colors ][ inputfiles ]
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.
- -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.
Does not deal correctly with greyscale alpha images with low bit depths, but
these wont benefit from quantizing.
Stuart Coyle <
[email protected]>
png(5)