pngquant(1) User Commands pngquant(1)

NAME

pngquant - PNG converter and lossy image compressor

SYNOPSIS

pngquant <options> [ncolors] file [file ...]
pngquant <options> [ncolors] - <file >file

DESCRIPTION

pngquant converts 32-bit RGBA PNGs to 8-bit (or smaller) RGBA-palette
PNGs, optionally using Floyd-Steinberg dithering. The output filename
is the same as the input name except that it ends in `-fs8.png' or
`-or8.png' (unless the input is stdin, in which case the quantized
image will go to stdout). The default behavior if the output file
exists is to skip the conversion; use --force to overwrite.

OPTIONS

-o out.png, --output out.png
Writes converted file to the given path. When this option is
used only single input file is allowed.

--ext new.png
File extension (suffix) to use for output files instead of the
default `-fs8.png' or `-or8.png'.

-f, --force
Overwrite existing output files. "--ext .png --force" can be
used to convert files in place (which is unsafe).

--nofs, --ordered
Disable Floyd-Steinberg dithering.

--floyd [=N]
Set dithering level using fractional number between 0 (none)
and 1 (full, the default).

-s N, --speed N
1 (brute-force) to 11 (fastest). The default is 3. Speed 10
has 5% lower quality, but is about 8 times faster than the
default. Speed 11 disables dithering and lowers compression
level.

-Q min-max, --quality min-max
min and max are numbers in range 0 (worst) to 100 (perfect),
similar to JPEG. pngquant will use the least amount of colors
required to meet or exceed the max quality. If conversion
results in quality below the min quality the image won't be
saved (or if outputting to stdin, 24-bit original will be
output) and pngquant will exit with status code 99.

--skip-if-larger
If conversion results in a file larger than the original, the
image won't be saved and pngquant will exit with status code
98. Additionally, file size gain must be greater than the
amount of quality lost. If quality drops by 50%, it will
expect 50% file size reduction to consider it worthwhile.

--posterize bits
Truncate number of least significant bits of color (per
channel). Use this when image will be output on low-depth
displays (e.g. 16-bit RGB). pngquant will make almost-opaque
pixels fully opaque and will reduce amount of semi-transparent
colors. When this option is enabled the default filename
suffix is `-ie-fs8.png' / `-ie-or8.png'.

--strip Remove optional chunks (metadata) from PNG files.

--transbug
Workaround for readers that expect fully transparent color to
be the last entry in the palette.

-v, --verbose
Enable verbose messages showing progress and information about
input/output. Opposite is --quiet. Errors are output to
stderr regardless of this option.

-V, --version
Display version on stdout and exit.

-h, --help
Display help and exit.

EXAMPLE

Creating a new image with the number of colors reduced to 64:

pngquant 64 image.png

The resulting image will have 64 colors and will be saved as
image-fs8.png.

Overwriting image in-place if it can be reduced without too much
quality loss:

pngquant -f --ext .png --quality 70-95 image.png

AUTHOR

pngquant is developed by Kornel Lesinski <kornel@pngquant.org> based on
code by Greg Roelofs <newt@pobox.com>.

pngquant homepage: https://pngquant.org.

2013-02-25