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MANUAL.txt
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oxipng 9.1.5 oxipng 10.0.0
Losslessly improve compression of PNG files Losslessly improve compression of PNG files
Usage: oxipng [OPTIONS] <files>... Usage: oxipng [OPTIONS] <files>...
@ -13,14 +13,14 @@ Options:
compression. Lower levels are faster, higher levels provide better compression, though compression. Lower levels are faster, higher levels provide better compression, though
with increasingly diminishing returns. with increasingly diminishing returns.
0 => --zc 5 --fast (1 trial, determined heuristically) 0 => --zc 5 --fast (filter chosen heuristically)
1 => --zc 10 --fast (1 trial, determined heuristically) 1 => --zc 10 --fast (filter chosen heuristically)
2 => --zc 11 -f 0,1,6,7 --fast (4 fast trials, 1 main trial) 2 => --zc 11 -f 0,1,6,7 --fast
3 => --zc 11 -f 0,7,8,9 (4 trials) 3 => --zc 11 -f 0,7,8,9 --brute-level 1 --brute-lines 3
4 => --zc 12 -f 0,7,8,9 (4 trials) 4 => --zc 12 -f 0,7,8,9 --brute-level 1 --brute-lines 4
5 => --zc 12 -f 0,1,2,5,6,7,8,9 (8 trials) 5 => --zc 12 -f 0,1,2,5,6,7,8,9 --brute-level 4 --brute-lines 4
6 => --zc 12 -f 0-9 (10 trials) 6 => --zc 12 -f 0-9 --brute-level 5 --brute-lines 8
max => (stable alias for the max level) max => (stable alias for the maximum level)
Manually specifying a compression option (zc, f, etc.) will override the optimization Manually specifying a compression option (zc, f, etc.) will override the optimization
preset, regardless of the order you write the arguments. preset, regardless of the order you write the arguments.
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-p, --preserve -p, --preserve
Preserve file permissions and timestamps if possible Preserve file permissions and timestamps if possible
-P, --pretend -d, --dry-run
Do not write any files, only show compression results Do not write any files, only show compression results
-s -s
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CAUTION: 'all' will convert APNGs to standard PNGs. CAUTION: 'all' will convert APNGs to standard PNGs.
Note that 'bKGD', 'sBIT' and 'hIST' will be forcibly stripped if the color type or bit Please note that regardless of any options set, some chunks will necessarily be stripped
depth is changed, regardless of any options set. when invalidated by the optimization:
bKGD, sBIT, hIST: Stripped if the color type or bit depth changes.
iDOT: Always stripped.
caBX: Stripped if it contains C2PA metadata. If explicitly retained by `--keep`,
optimization will be aborted.
The default when --strip is not passed is to keep all metadata. The default when --strip is not passed is to keep all chunks that remain valid.
--keep <list> --keep <list>
Strip all metadata chunks except those in the comma-separated list. The special value Strip all metadata chunks except those in the comma-separated list. The special value
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but take care as while this is “visually lossless”, it is technically a lossy but take care as while this is “visually lossless”, it is technically a lossy
transformation and may be unsuitable for some applications. transformation and may be unsuitable for some applications.
-i, --interlace <type> -i, --interlace <mode>
Set the PNG interlacing type, where <type> is one of: Set the PNG interlacing mode, where <mode> is one of:
0 => Remove interlacing from all images that are processed off => Remove interlacing from all images that are processed
1 => Apply Adam7 interlacing on all images that are processed on => Apply Adam7 interlacing on all images that are processed
keep => Keep the existing interlacing type of each image keep => Keep the existing interlacing mode of each image
Note that interlacing can add 25-50% to the size of an optimized image. Only use it if you Note that interlacing can add 25-50% to the size of an optimized image. Only use it if you
believe the benefits outweigh the costs for your use case. believe the benefits outweigh the costs for your use case.
[default: 0] [default: off]
--scale16 --scale16
Forcibly reduce images with 16 bits per channel to 8 bits per channel. This is a lossy Forcibly reduce images with 16 bits per channel to 8 bits per channel. This is a lossy
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Heuristic strategies (try to find the best delta filter for each line) Heuristic strategies (try to find the best delta filter for each line)
5 => MinSum Minimum sum of absolute differences 5 => MinSum Minimum sum of absolute differences
6 => Entropy Highest Shannon entropy 6 => Entropy Smallest Shannon entropy
7 => Bigrams Lowest count of distinct bigrams 7 => Bigrams Lowest count of distinct bigrams
8 => BigEnt Highest Shannon entropy of bigrams 8 => BigEnt Smallest Shannon entropy of bigrams
9 => Brute Smallest compressed size (slow) 9 => Brute Smallest compressed size (slow)
The default value depends on the optimization level preset. The default value depends on the optimization level preset.
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--fix --fix
Do not perform checksum validation of PNG chunks. This may allow some files with errors to Do not perform checksum validation of PNG chunks. This may allow some files with errors to
be processed successfully. be processed successfully. The output will always have correct checksums.
--force --force
Write the output even if it is larger than the input Write the output even if it is larger than the input
-Z, --zopfli -z, --zopfli
Use the much slower but stronger Zopfli compressor for main compression trials. Use the much slower but stronger Zopfli compressor for main compression trials.
Recommended use is with '-o max' and '--fast'. Recommended use is with '-o max' and '--fast'.
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[default: 15] [default: 15]
--ziwi <iterations>
Stop Zopfli compression after this number of iterations without improvement. Use this in
conjunction with a high value for '--zi' to achieve better compression in reasonable time.
--brute-level <level>
Set the libdeflate compression level to use with the Brute filter strategy. Sane values
are 1-5. Higher values are not necessarily better.
--brute-lines <lines>
Set the number of lines to compress at once with the Brute filter strategy. Sane values
are 2-16. Higher values are not necessarily better.
--timeout <secs> --timeout <secs>
Maximum amount of time, in seconds, to spend on optimizations. Oxipng will check the Maximum amount of time, in seconds, to spend on optimizations. Oxipng will check the
timeout before each transformation or compression trial, and will stop trying to optimize timeout before each transformation or compression trial, and will stop trying to optimize
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are already in progress, so it is currently of limited effectiveness for large files with are already in progress, so it is currently of limited effectiveness for large files with
high compression levels. high compression levels.
--max-raw-size <bytes>
Maximum size to allow for the input image. If the raw, decompressed image data (or the
file size) of the image exceeds this size, it will be skipped. This is useful for limiting
memory usage or avoiding long processing times on large images. The value may be specified
with a unit suffix such as k, KB, m, MB, etc.
The decompressed size of an image is roughly equal to width * height * bit-depth / 8. E.g.
a 1920x1080 image with 24-bit color depth would be roughly 6MB.
-t, --threads <num> -t, --threads <num>
Set the maximum number of threads to use. Oxipng uses multithreading to evaluate multiple Set the maximum number of threads to use. Oxipng uses multithreading to evaluate multiple
optimizations on the same file in parallel as well as process multiple files in parallel. optimizations on the same file in parallel as well as process multiple files in parallel.