1\" Process this file with
2.\" groff -man -Tascii foo.1
3.\"
4.TH PNGNQ 1 "MAY 2009" Linux "User Manuals"
5.SH NAME
6pngnq \- quantize png images
7.SH SYNOPSIS
8.B pngnq [-vfhV][-s
9.I sample_factor
10.B ][-Q
11.I dither
12.B ][-g
13.I gamma
14.B ][-e
15.I extension
16.B ][-d
17.I dir
18.B ][-n
19.I colors
20.B ][
21.I inputfiles
22.B ]
23.SH DESCRIPTION
24.B pngnq
25Quantizes a 32-bit RGBA PNG image to an 8 bit RGBA palette PNG
26using the neuquant algorithm. The output file name is the
27input file name extended with "-nq8.png" or a specified extension.
28
29.SH OPTIONS
30.IP -v
31Verbose mode. Prints status messages.
32.IP -f
33Force ovewriting of files.
34.IP "-s sample factor"
35Sample factor. The neuquant algorithm samples pixels stepping by this value.
36The default value of 3 gives good results. Higher values sample less
37of the image pixels and thus are faster but less accurate. A factor of 1 samples
38every image pixel.
39.IP "-n colors"
40Specifies the number of colors to quantize to. Defaults to 256 which is the maximum.
41The minimum here is 2.
42.IP "-Q dither"
43Choose a dithering method: n = no dither (default), f = Floyd Steinberg dithering.
44.IP "-g gamma"
45Set the image gamma correction. If not present, uses the png file's gamma or defaults to 1.0.
46.IP "-e extension"
47Specifies the new filename extension. Defaults to "-nq8.png".
48Pngnq drops .png from the original filenames. If you set the argument of the -e option
49to .png and choose the -f option the input file will be overwritten.
50.IP "-d dir"
51Tells pngnq to put output files in a directory other than the one the input files
52are in.
53.IP "input files"
54The png files to be processed. Defaults to standard input if not specified.
55If standard input is being processed the output is sent to standard output.
56.IP -h
57Print program help.
58.IP -V
59Print version number and library versions.
60
61.SH BUGS
62Does not deal correctly with greyscale alpha images with low bit depths, but these wont benefit from quantizing.
63
64.SH AUTHOR
65Stuart Coyle <stuart.coyle@gmail.com>
66.SH "SEE ALSO"
67.BR png(5)
68