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oxipng(1) General Commands Manual oxipng(1) NAME oxipng - Losslessly improve compression of PNG files SYNOPSIS oxipng [-o|--opt] [-r|--recursive] [--dir] [--out] [--stdout] [-p|--preserve] [-d|--dry-run] [-s ] [--strip] [--keep] [-a|--alpha] [-i|--interlace] [--scale16] [-v|--verbose]... [-q|--quiet] [-f|--fil- ters] [--fast] [--zc] [--nb] [--nc] [--np] [--ng] [--nx] [--nz] [--fix] [--force] [-z|--zopfli] [--zi] [--ziwi] [--brute-level] [--brute-lines] [--timeout] [--max-raw-size] [-t|--threads] [--sequential] [-h|--help] [-V|--version] <files> DESCRIPTION Losslessly improve compression of PNG files OPTIONS -o, --opt <level> [default: 2] Set the optimization level preset. The default level 2 is quite fast and provides good compression. Lower levels are faster, higher levels provide better compression, though with increas- ingly diminishing returns. 0 => --zc 5 --fast (filter chosen heuristi- cally) 1 => --zc 10 --fast (filter chosen heuristi- cally) 2 => --zc 11 -f 0,1,6,7 --fast 3 => --zc 11 -f 0,7,8,9 --brute-level 1 --brute-lines 3 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 --brute-level 4 --brute-lines 4 6 => --zc 12 -f 0-9 --brute-level 5 --brute-lines 8 max => (stable alias for the maximum level) Manually specifying a compression option (zc, f, etc.) will override the optimization preset, regardless of the order you write the arguments. -r, --recursive When directories are given as input, traverse the directory trees and optimize all PNG files found (files with .png or .apng extension). --dir <directory> Write output file(s) to <directory>. If the directory does not exist, it will be created. Note that this will not preserve the directory structure of the input files when used with '--recur- sive'. --out <file> Write output file to <file> --stdout Write output to stdout -p, --preserve Preserve file permissions and timestamps if possible -d, --dry-run Do not write any files, only show compression results -s Strip safely-removable chunks, same as '--strip safe' --strip <mode> Strip metadata chunks, where <mode> is one of: safe => Strip all non-critical chunks, except for the following: cICP, iCCP, sRGB, pHYs, acTL, fcTL, fdAT all => Strip all non-critical chunks <list> => Strip chunks in the comma-separated list, e.g. 'bKGD,cHRM' CAUTION: 'all' will convert APNGs to standard PNGs. Please note that regardless of any options set, some chunks will necessarily be stripped 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 chunks that remain valid. --keep <list> Strip all metadata chunks except those in the comma-separated list. The special value 'display' includes chunks that affect the image appearance, equivalent to '--strip safe'. E.g. '--keep eXIf,display' will strip chunks, keeping only eXIf and those that affect the image appearance. -a, --alpha Perform additional optimization on images with an alpha channel, by altering the color values of fully transparent pixels. This is generally recommended for better compression, but take care as while this is visually lossless, it is technically a lossy transformation and may be unsuitable for some applications. -i, --interlace <mode> [default: off] Set the PNG interlacing mode, where <mode> is one of: off => Remove interlacing from all images that are processed on => Apply Adam7 interlacing on all images that are processed 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 believe the benefits outweigh the costs for your use case. --scale16 Forcibly reduce images with 16 bits per channel to 8 bits per channel. This is a lossy operation but can provide significant savings when you have no need for higher depth. Reduction is performed by scaling the values such that, e.g. 0x00FF is re- duced to 0x01 rather than 0x00. Without this flag, 16-bit images will only be reduced in depth if it can be done losslessly. -v, --verbose Run in verbose mode (use twice to increase verbosity) -q, --quiet Run in quiet mode -f, --filters <list> Perform compression trials with each of the given filter types. You can specify a comma-separated list, or a range of values. E.g. '-f 0-3' is the same as '-f 0,1,2,3'. PNG delta filters (apply the same filter to every line) 0 => None (recommended to always include this filter) 1 => Sub 2 => Up 3 => Average 4 => Paeth Heuristic strategies (try to find the best delta filter for each line) 5 => MinSum Minimum sum of absolute differences 6 => Entropy Smallest Shannon entropy 7 => Bigrams Lowest count of distinct bigrams 8 => BigEnt Smallest Shannon entropy of bigrams 9 => Brute Smallest compressed size (slow) The default value depends on the optimization level preset. --fast Perform a fast compression evaluation of each enabled filter, followed by a single main compression trial of the best result. Recommended if you have more filters enabled than CPU cores. --zc <level> Deflate compression level (0-12) for main compression trials. The levels here are defined by the libdeflate compression li- brary. The default value depends on the optimization level preset. --nb Do not change bit depth --nc Do not change color type --np Do not change color palette --ng Do not change to or from grayscale --nx Do not perform any transformations and do not deinterlace by de- fault. --nz Do not recompress IDAT unless required due to transformations. Recompression of other compressed chunks (such as iCCP) will also be disabled. Note that the combination of '--nx' and '--nz' will fully disable all optimization. --fix Do not perform checksum validation of PNG chunks. This may allow some files with errors to be processed successfully. The output will always have correct checksums. --force Write the output even if it is larger than the input -z, --zopfli Use the much slower but stronger Zopfli compressor for main com- pression trials. Recommended use is with '-o max' and '--fast'. --zi <iterations> [default: 15] Set the number of iterations to use for Zopfli compression. Us- ing fewer iterations may speed up compression for large files. This option requires '--zopfli' to be set. --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 fil- ter strategy. Sane values are 1-5. Higher values are not neces- sarily better. --brute-lines <lines> Set the number of lines to compress at once with the Brute fil- ter strategy. Sane values are 2-16. Higher values are not neces- sarily better. --timeout <secs> Maximum amount of time, in seconds, to spend on optimizations. Oxipng will check the timeout before each transformation or com- pression trial, and will stop trying to optimize the file if the timeout is exceeded. Note that this does not cut short any oper- ations that are already in progress, so it is currently of lim- ited effectiveness for large files with high compression levels. --max-raw-size <bytes> Maximum size to allow for the input image. If the raw, decom- pressed image data (or the file size) of the image exceeds this size, it will be skipped. This is useful for limiting memory us- age 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> Set the maximum number of threads to use. Oxipng uses multi- threading to evaluate multiple optimizations on the same file in parallel as well as process multiple files in parallel. You can set this to a lower value if you need to limit memory or CPU us- age. [default: num logical CPUs] --sequential Process multiple files sequentially rather than in parallel. Use this if you need determinism in the processing order. Note this is not necessary if using '--threads 1'. -h, --help Print help (see a summary with '-h') -V, --version Print version <files> File(s) to compress (use '-' for stdin) VERSION v0.1.0 AUTHORS Joshua Holmer <jholmer.in@gmail.com> oxipng 0.1.0 oxipng(1)
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | VERSION | AUTHORS
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