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OPT-PNG

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
EXAMPLES
NOTES
SEE ALSO
COPYRIGHT

NAME

opt-png − losslessly optimize PNG image files

SYNOPSIS

opt-png [−g(ray)] [−h(elp)] [−q(uiet)] [−r(es) DPI] [−t(ouch)] file...

DESCRIPTION

opt-png losslessly optimizes PNG images by removing unused palette entries and/or optimizing the filtering algorithm. This is accomplished using a combination of the filesize, pngcrush, pngrecolor, pngstrip, and tempname utilities.

OPTIONS

−g

Force output to grayscale.

−h

Print help and quit.

−q

Quiet output. No output commentary will be printed.

−r DPI

Write the specified resolution into the pHYs chunk of the output file. Units are in pixels-per-inch. To convert from pixels-per-meter, multiply by 0.0254 (or divide by 39.37). Note that this does not change the number of pixels in the image. It only changes the assumed size of the pixels.

−t

Preserve timestamp on modified files.

EXAMPLES

Optimize a couple of image files:

opt-png image001.png image002.png

Optimize all PNG images in an entire directory tree:

find . -name "*.png" -exec opt-png {} \;

Or alternatively, optimize all PNG images this way:

find . -name "*.png" -print0 | xargs -0 opt-png

Fully utilize a quad-core system while optimizing all PNG images:

find . -name "*.png" -print0 | xargs -0 -n 1 -P 4 opt-png
find . -name "*.png" | parallel opt-png

NOTES

If at all possible, make sure that pngcrush version 1.6.x or later is running on your computer. It performs substantially better than pngcrush 1.5.10 (and earlier) on black-and-white (and other low-color) images due to use of the Z_RLE zlib strategy.

SEE ALSO

filesize(1), pngcrush(1), pngrecolor(1), pngstrip(1), tempname(1)

COPYRIGHT

Copyright (C) 2004-2021 by Brian Lindholm. This program is free software; you can use it, redistribute it, and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.