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.

                                        November 30, 2024