{"id":15296324,"url":"https://github.com/galsim-developers/galsim","last_synced_at":"2026-02-23T00:50:13.338Z","repository":{"id":2533923,"uuid":"3510804","full_name":"GalSim-developers/GalSim","owner":"GalSim-developers","description":"The modular galaxy image simulation toolkit.  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The bulk of the calculations are\ncarried out in C++, and the user interface is in Python.  In addition, the code\ncan operate directly on \"config\" files, for those users who prefer not to work\nin Python.  The impetus for the software package was a weak lensing community\ndata challenge, called GREAT3:\n\n    https://github.com/barnabytprowe/great3-public\n\nHowever, the code has numerous additional capabilities beyond those needed for\nthe challenge, and has been useful for a number of projects that needed to\nsimulate high-fidelity galaxy images with accurate sizes and shears.  At the\nend of this file, there is a list of the code capabilities and plans for future\ndevelopment.  For details of algorithms and code validation, please see\n\n    http://adsabs.harvard.edu/abs/2015A%26C....10..121R\n\nThe GalSim version numbering tries to follow `Semantic Versioning \u003chttps://semver.org/\u003e`_\nThis means that releases are numbered as M.m.r, where M is a major version number,\nm is the minor version, and r is the revision (or patch or bugfix) number.\n\nThe public API is preserved within a given major version number.  So code that works\nwith version 2.2.3 (say) should continue to work for all subsequent 2.x.x versions.\nMinor versions indicate new features being added to the API.  Revision versions\ndon't add any new features, but fix bugs in the previous release.\n\nBasic Installation\n==================\n\nNormally, to install GalSim, you should just need to run::\n\n    pip install galsim\n\nDepending on your setup, you may need to add either sudo to the start\nor --user to the end of this command as you normally do when pip installing\npackages.\n\nSee `Installation Instructions` for full details including one dependency (FFTW) that is not\npip installable, so you may need to install before running this command.\n\nYou can also use conda via conda-forge::\n\n    conda install -c conda-forge galsim\n\n\nSource Distribution\n===================\n\nTo get the latest version of the code, you can grab the tarball (or zip file) from\n\nhttps://github.com/GalSim-developers/GalSim/releases/\n\nAlso, feel free to fork the repository:\n\nhttps://github.com/GalSim-developers/GalSim/fork\n\nOr clone the repository with either of the following::\n\n    git clone git@github.com:GalSim-developers/GalSim.git\n    git clone https://github.com/GalSim-developers/GalSim.git\n\nThe code is also distributed via Fink, Macports, and Homebrew for Mac users.\nSee `Installation Instructions` (in INSTALL.rst) for more information.\n\nThe code is licensed under a BSD-style license.  See the file LICENSE for more\ndetails.\n\n\nKeeping up-to-date with GalSim\n==============================\n\nThere is a GalSim mailing list, organized through the Google Group\ngalsim-announce.  Members of the group will receive news and updates about the\nGalSim code, including notifications of major version releases, new features\nand bugfixes.\n\nYou do not need a Google Account to subscribe to the group, simply send any\nemail to::\n\n    galsim-announce+subscribe@googlegroups.com\n\nIf you receive a confirmation request (check junk mail filters!) simply reply\ndirectly to that email, with anything, to confirm.  You may also click the link\nin the confirmation request, but you may be asked for a Google Account login.\n\nTo unsubscribe, simply send any email to::\n\n    galsim-announce+unsubscribe@googlegroups.com\n\nYou should receive notification that your unsubscription was successful.\n\n\nHow to communicate with the GalSim developers\n=============================================\n\nCurrently, the lead developers for GalSim are:\n\n  - Mike Jarvis (mikejarvis17 at gmail)\n  - Rachel Mandelbaum (rmandelb at andrew dot cmu dot edu)\n  - Josh Meyers (jmeyers314 at gmail)\n\nHowever, many others have contributed to GalSim over the years as well, for\nwhich we are very grateful.\n\nIf you have a question about how to use GalSim, a good place to ask it is at\n`StackOverflow \u003chttp://stackoverflow.com/\u003e`_.  Some of the GalSim developers\nhave alerts set up to be automatically notified about questions with the\n'galsim' tag, so there is a good chance that your question will be answered.\n\nIf you have any trouble installing or using the code, or find a bug, or have a\nsuggestion for a new feature, please open up an Issue on our `GitHub\nrepository \u003chttps://github.com/GalSim-developers/GalSim/issues\u003e`_.  We also accept\npull requests if you have something you'd like to contribute to the code base.\n\nIf none of these communication avenues seem appropriate, you can also contact\nus directly at the above email addresses.\n\n\nDemonstration scripts\n=====================\n\nThere are a number of scripts in ``examples/`` that demonstrate how the code can\nbe used.  These are called ``demo1.py`` ... ``demo13.py``.  You can run them by\ntyping (e.g.) ``python demo1.py`` while sitting in ``examples/``, All demo scripts\nare designed to be run in the ``examples/`` directory.  Some of them access\nfiles in subdirectories of the ``examples/`` directory, so they would not work\ncorrectly from other locations.\n\nA completely parallel sequence of configuration files, called ``demo1.yaml`` ...\n``demo13.yaml``, demonstrates how to make the same set of simulations using\nconfig files that are parsed by the executable ``bin/galsim``.\n\nTwo other scripts in the ``examples/`` directory that may be of interest, but\nare not part of the GalSim tutorial series, are ``make_coadd.py``, which\ndemonstrates the use of the FourierSqrt transformation to optimally coadd\nimages, and ``psf_wf_movie.py``, which demonstrates the realistic atmospheric\nPSF code by making a movie of a time-variable PSF and wavefront.\n\nAs the project develops through further versions, and adds further\ncapabilities to the software, more demo scripts may be added to ``examples/``\nto illustrate what GalSim can do.\n\n\nSummary of current capabilities\n===============================\n\nCurrently, GalSim has the following capabilities:\n\n* Can generate PSFs from a variety of simple parametric models such as Moffat,\n  Kolmogorov, and Airy, as well as an optical PSF model that includes Zernike\n  aberrations to arbitrary order, and an optional central obscuration and\n  struts.\n\n* Can simulate galaxies from a variety of simple parametric models as well as\n  from real HST data.  For information about downloading a suite of COSMOS\n  images, see\n\n  https://github.com/GalSim-developers/GalSim/wiki/RealGalaxy%20Data\n\n* Can simulate atmospheric PSFs from realistic turbulent phase screens.\n\n* Can make the images either via i) Fourier transform, ii) real-space\n  convolution (real-space being occasionally faster than Fourier), or\n  iii) photon-shooting.  The exception is that objects that include a\n  deconvolution (such as RealGalaxy objects) must be carried out using Fourier\n  methods only.\n\n* Can handle wavelength-dependent profiles and integrate over filter\n  bandpasses appropriately, including handling wavlengths properly when\n  photon shooting.\n\n* Can apply shear, magnification, dilation, or rotation to a galaxy profile\n  including lensing-based models from a power spectrum or NFW halo profile.\n\n* Can draw galaxy images into arbitrary locations within a larger image.\n\n* Can add noise using a variety of noise models, including correlated noise.\n\n* Can whiten or apply N-fold symmetry to existing correlated noise that is\n  already in an image.\n\n* Can read in input values from a catalog, a dictionary file (such as a JSON\n  or YAML file), or a fits header.\n\n* Can write images in a variety of formats: regular FITS files, FITS data\n  cubes, or multi-extension FITS files.  It can also compress the output files\n  using various compressions including gzip, bzip2, and rice.\n\n* Can carry out nearly any simulation that a user might want using two parallel\n  methods: directly using Python code, or by specifying the simulation\n  properties in an input configuration script.  See the demo scripts in\n  the examples/ directory for examples of each.\n\n* Supports a variety of possible WCS options from a simple pixel scale factor\n  of arcsec/pixel to affine transforms to arbitrary functions of (x,y),\n  including a variety of common FITS WCS specifications.\n\n* Can include a range of simple detector effects such as nonlinearity,\n  brighter-fatter effect, etc.\n\n* Has a module that is particularly meant to simulate images for the Roman\n  Space Telescope.\n\n\nPlanned future development\n--------------------------\n\nWe plan to add the following additional capabilities in future versions of\nGalSim:\n\n* Simulating more sophisticated detector defects and image artifacts.  E.g.\n  vignetting, fringing, cosmic rays, saturation, bleeding, ... (cf. Issues\n  #553, #828)\n\n* Proper modeling of extinction due to dust. (cf. Issues #541, #550)\n\n* More kinds of realistic galaxies. (cf. Issues #669, #795, #808)\n\n* Various speed improvements.  (cf. Issues #205, #566, #875)\n\nThere are many others as well.  Please see\n\nhttps://github.com/GalSim-developers/GalSim/issues\n\nfor a list of the current open issues.  And feel free to add an issue if there\nis something useful that you think should be possible, but is not currently\nimplemented.\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fgalsim-developers%2Fgalsim","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fgalsim-developers%2Fgalsim","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fgalsim-developers%2Fgalsim/lists"}