130 lines
3.5 KiB
Groff
130 lines
3.5 KiB
Groff
.Dd 2013-02-25
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.Dt pngquant 1
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.Sh NAME
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.Nm pngquant
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.Nd PNG converter and lossy image compressor
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.Sh SYNOPSIS
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.Nm
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.Aq options
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.Op ncolors
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.Pa file
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.Op Ar
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.Nm
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.Aq options
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.Op ncolors
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.Fl
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.Cm < Ns Pa file
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.Cm > Ns Pa file
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.Sh DESCRIPTION
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.Nm
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converts 32-bit RGBA PNGs to 8-bit (or smaller) RGBA-palette PNGs, optionally using Floyd-Steinberg dithering.
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The output filename is the same as the input name except that it ends in
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.Ql -fs8.png
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or
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.Ql -or8.png
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(unless the input is stdin, in which case the quantized image will go to stdout).
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The default behavior if the output file exists is to skip the conversion; use
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.Fl Fl force
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to overwrite.
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.Sh OPTIONS
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.Bl -tag -width -indent
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.It Fl o Ar out.png , Fl Fl output Ar out.png
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Writes converted file to the given path. When this option is used only single input file is allowed.
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.It Fl Fl ext Ar new.png
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File extension (suffix) to use for output files instead of the default
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.Ql -fs8.png
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or
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.Ql -or8.png .
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.It Fl f , Fl Fl force
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Overwrite existing output files.
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.Do
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.Fl Fl ext
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.Ar .png
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.Fl Fl force
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.Dc
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can be used to convert files in place (which is unsafe).
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.It Fl Fl nofs , Fl Fl ordered
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Disable Floyd-Steinberg dithering.
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.It Fl Fl floyd Op Ar =N
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Set dithering level using fractional number between
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.Cm 0
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(none) and
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.Cm 1
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(full, the default).
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.It Fl s Ar N , Fl Fl speed Ar N
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.Cm 1
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(brute-force) to
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.Cm 11
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(fastest). The default is
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.Cm 3 .
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Speed
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.Cm 10
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has 5% lower quality, but is about 8 times faster than the default. Speed 11 disables dithering and lowers compression level.
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.It Fl Q Ar min-max , Fl Fl quality Ar min-max
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.Va min
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and
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.Va max
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are numbers in range
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.Cm 0
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(worst) to
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.Cm 100
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(perfect), similar to JPEG.
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.Nm
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will use the least amount of colors required to meet or exceed the
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.Va max
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quality. If conversion results in quality below the
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.Va min
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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
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.Er 99 .
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.It Fl Fl skip-if-larger
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If conversion results in a file larger than the original the image won't be saved and pngquant will exit with status code
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.Er 98 .
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Additionally, file size gain must be greater than the amount of quality lost.
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.It Fl Fl posterize Ar bits
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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).
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.It Fl Fl iebug
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Workaround for Internet Explorer 6, which only displays fully opaque pixels.
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.Nm
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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
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.Ql -ie-fs8.png
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/
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.Ql -ie-or8.png .
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.It Fl Fl transbug
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Workaround for readers that expect fully transparent color to be the last entry in the palette.
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.It Fl v , Fl Fl verbose
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Enable verbose messages showing progress and information about input/output. Opposite is
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.Fl Fl quiet .
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Errors are output to
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.Pa stderr
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regardless of this option.
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.It Fl V , Fl Fl version
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Display version on
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.Pa stdout
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and exit.
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.It Fl h , Fl Fl help
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Display help and exit.
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.El
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.Sh EXAMPLE
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Creating a new image with the number of colors reduced to 64:
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.Bd -ragged -offset indent
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.Nm
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.Cm 64 image.png
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.Ed
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.Pp
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The resulting image will have 64 colors and will be saved as
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.Pa image-fs8.png .
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.Pp
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Overwriting image in-place if it can be reduced without too much quality loss:
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.Bd -ragged -offset indent
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.Nm
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.Cm -f --ext .png --quality 70-95 image.png
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.Ed
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.Sh AUTHOR
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.Nm
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is developed by Kornel Lesinski
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.Aq Mt kornel@pngquant.org
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based on code by Greg Roelofs
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.Aq Mt newt@pobox.com .
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.Pp
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.Lk http://pngquant.org "pngquant homepage" .
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