Montage (http://montage.ipac.caltech.edu) is an Open Source toolkit, distributed with a BSD 3-clause license, for assembling Flexible Image Transport System (FITS) images into mosaics according to the user's custom specifications of coordinates, projection, spatial sampling and rotation.
The toolkit contains utilities for reprojecting and background matching images, assembling them into mosaics, visualizing the results, and discovering, analyzing and understanding image metadata from archives or the user's images.
Montage is written in ANSI-C and is portable across all common Unix-like platforms, including Linux, Solaris, Mac OSX and Cygwin on Windows. The package provides both stand-alone executables and the same functionality in library form. It has been cross-compiled to provide native Windows executables and packaged as a binary Python extension (available via "pip install MontagePy").
The distribution contains all libraries needed to build the toolkit from a single simple "make" command, including CFITSIO and the WCS library (which has been extended to support HEALPix and World-Wide Telescope TOAST projections. The toolkit is in wide use in astronomy to support research projects, and to support pipeline development, product generation and image visualization for major projects and missions; e.g. Spitzer Space Telescope, Herschel, Kepler, AKARI and others. Montage is used as an exemplar application by the computer science community in developing next-generation cyberinfrastructure, especially workflow frameworks on distributed platforms, including multiple clouds.
Montage provides multiple reprojection algorithms optimized for different needs, maximizing alternately flux conservation, range of projections, and speed.
The visualization module supports full (three-color) display of FITS images and publication quality overlays of catalogs (scaled symbols), image metadata, and coordinate grids. It fits in equally well in pipelines or as the basis for interactive image exploration and there is Python support for the latter (It has also been used in web/Javascript applications).
Montage was funded from 2002 to 2005 by the National Aeronautics and Space Administration's Earth Science Technology Office, Computation Technologies Project, under Cooperative Agreement Number NCC5-626 between NASA and the California Institute of Technology. The Montage distribution includes an adaptation of the MOPEX algorithm developed at the Spitzer Science Center. Montage is now funded by the National Science Foundation under Award Number NSF ACI-1440620.