pngnq(1)
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.
