SEGMENT(1)

📦
version 0.24 · 5 versions
, in epel 10, epel 9, nixos 26.05, nixpkgs unstable, ubuntu resolute, ubuntu stonking

💖 SEGMENT(1) 💖

okay bestie, gather round, because this is the manual page for Segment — part of the astsegment situation — and it lives in the User Commands corner of the GNU Astronomy Utilities 0.24 universe. she's giving ✨segmentation based on signal structure✨ and honestly? iconic.

🌸 NAME 🌸

Segment — segmentation based on signal structure. that's the whole vibe. 💅

🎀 SYNOPSIS 🎀

astsegment [OPTION...] ASTRdata

🦋 DESCRIPTION 🦋

so Segment is part of GNU Astronomy Utilities 0.24, and what she does is take an initially labeled region and segment it based on the structure inside the signal. the whole process is like a little three-act play:

  1. she finds the true clumps (local maxima),
  2. figures out which ones have strong connections,
  3. then grows them out until they cover the full area of each detection.

slay.

for more info, you can run any of these commands. and lowkey, the second one is the main character — it has a very comprehensive explanation of how Segment gets invoked: expected input(s), output(s), and a full rundown of every single option. no cap.

all options and their values:

$ astsegment -P

inputs/outputs and options:

$ info astsegment

full section in the manual/book:

$ info Segment

full Gnuastro manual/book:

$ info gnuastro

and if the manual is not giving what you need, you can get direct help from experienced Gnuastro users and developers. for that, run:

$ info help-gnuastro

✨ OPTIONS ✨

Segment options:

🌈 Input:

  • --chdu=STR — HDU/extension of the convolved image inside the file.
  • --convolved=FITS — a convolved image file, so you can skip the whole convolution thing.
  • --dhdu=STR — the HDU that holds the detection image.
  • -d, --detection=FITS — filename of the detection image (the one getting segmented).
  • -h, --hdu=STR/INT — the HDU holding the values (aka the science image).
  • --khdu=STR — the HDU holding the kernel image.
  • -k, --kernel=FITS — filename of the kernel you want to convolve with the input.
  • --sky=STR/FLT — filename of the Sky values image you want subtracted.
  • --skyhdu=STR — the HDU containing the Sky value to subtract.
  • --std=STR/FLT — filename of the Sky standard deviation.
  • --stdhdu=STR — the HDU containing the Sky standard deviation.
  • --variance — plot twist: the STD input is actually variance.

🧚 Tessellation (tile grid):

  • --checktiles — tile IDs in an image, sized the same as the input.
  • -F, --remainderfrac=FLT — fraction of the remainder to split off for the last tile.
  • --interpmetric=STR — interpolation metric (radial, manhattan).
  • --interpnumngb=INT — number of neighbors to use for interpolation.
  • --interponlyblank — only interpolate over the blank tiles. nothing else. mind your business.
  • -L, --largetilesize=INT[,INT] — same energy as --tilesize, but for the larger tiles.
  • -M, --numchannels=INT[,..] — number of channels in dim.s (FITS order).
  • --oneelempertile — display 1 element per tile, not the full input resolution.
  • --workoverch — work over channel edges (as a whole, not tile by tile).
  • -Z, --tilesize=INT[,INT] — regular tile size on dim.s (FITS order).

💜 Output:

  • -D, --dontdelete — don't delete the output if it already exists. she's stubborn like that.
  • -K, --keepinputdir — keep the input directory for the automatic output.
  • --noobjects — finish with true clumps only, don't make objects.
  • --outfitsnocommit — no Git commit in the 0-th HDU of the output FITS.
  • --outfitsnoconfig — no metadata in the 0-th HDU of the output FITS.
  • --outfitsnodate — no 'DATE' in the 0-th HDU of the output FITS.
  • --outfitsnoversions — no versions in the 0-th HDU of the output FITS.
  • -o, --output=STR — output file name.
  • --rawoutput — output contains only CLUMPS and/or OBJECTS HDUs.
  • --tableformat=STR — 'txt', 'fits-ascii', 'fits-binary'.
  • --wcslinearmatrix=STR — WCS linear matrix of the output ('pc' or 'cd').

🍓 Segmentation:

  • -B, --minskyfrac=FLT — minimum fraction of undetected area allowed in a tile.
  • --checksegmentation — store the segmentation steps into a file.
  • --checksn — save the clump S/N values into a file.
  • -c, --snquant=FLT — S/N quantile of the true sky clumps.
  • --grownclumps — save the grown clumps instead of the original ones.
  • -G, --gthresh=FLT — multiple of STD at which to stop growing clumps.
  • --minima — build internal clumps from minima.
  • --minnumfalse=INT — minimum number for S/N estimation.
  • -m, --snminarea=INT — minimum area of clumps for S/N estimation.
  • -O, --objbordersn=FLT — minimum S/N for grown clumps to count as one object.
  • -s, --clumpsnthresh=FLT — S/N threshold of true clumps.
  • -v, --keepmaxnearriver — keep clumps whose peak is touching a river. 🏞️
  • -y, --minriverlength=INT — minimum length of useful grown clump rivers.

👑 Operating modes:

  • -?, --help — give this help list.
  • --checkconfig — list all config files and variables that were read.
  • --cite — BibTeX citation for this program. cite your sources, bestie.
  • --config=STR — read configuration file STR immediately.
  • --config-prefix=STR — custom prefix of option names in config files.
  • -C, --continueaftercheck — continue processing after the checks.
  • --lastconfig — do not parse any more configuration files.
  • --minmapsize=INT — minimum bytes to avoid RAM automatically.
  • -N, --numthreads=INT — number of CPU threads to use.
  • --onlyversion=STR — only run if the program version is STR.
  • -P, --printparams — print the parameter values that would be used, then abort.
  • --quietmmap — don't print the mmap'd file's name and size.
  • -q, --quiet — only report errors, stay quiet about the steps.
  • -S, --setdirconf — set default values for this directory, then abort.
  • --usage — give a short usage message.
  • -U, --setusrconf — set default values for this user, then abort.
  • -V, --version — print program version.
💀 heads up: mandatory or optional arguments to long options are also mandatory or optional for any corresponding short options. yes, the short ones inherit the drama.

GNU Astronomy Utilities home page: http://www.gnu.org/software/gnuastro/

🙈 REPORTING BUGS 🙈

found a bug? report it to bug-gnuastro@gnu.org. don't be shy, they're nice about it. 🫶

Copyright © 2015-2025 Free Software Foundation, Inc. License GPLv3+: GNU General public license version 3 or later.

This is free software: you are free to change and redistribute it.

There is NO WARRANTY, to the extent permitted by law.

Written/developed by Mohammad Akhlaghi. king behavior, honestly. 👑

💫 SEE ALSO 💫

The full documentation for Segment is maintained as a Texinfo manual. If the info and Segment programs are properly installed at your site, the command

info Segment

should give you access to the complete manual.

and that's the whole page, bestie 💖 this was GNU Astronomy Utilities 0.24, dated November 2025 — go segment something gorgeous. periodt. 🎀✨🦋

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