The following software packages display or manipulate the relatively simple class of FITS data files that containing 2-dimensional images, often of celestial objects in the night sky. It should be noted that FITS is a very general data format that is used for many different types of astronomical data sets, so these packages are not necessarily capable of reading every type of FITS file. Developers of new image display programs should be aware of the special requirements for effectively displaying FITS images.
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FITS Image Software Packages
for image viewing, analysis, and format conversion
FITS Image Viewers
- Image viewers for PC and Macs - an extensive listing of commercial and freeware image processing software compiled by the Astronomy Education Committee.
- Aladin - Interactive Sky Atlas
- APLpy - Astronomical Plotting Library in Python is a Python module aimed at producing publication-quality plots of astronomical imaging data in FITS format.
- Aperture Photometry Tool - interactive software tool for visualizing and performing aperture photometry measurements on astronomical images.
- Avis FITS Viewer - a FITS viewer for Windows. Only reads 8 and 16 bit FITS images. Converts to RAW, TIF, TGA, BMP, and JPEG formats
- ds9 (SAOImage ) - astronomical visualization application from SAO
- FITS Liberator - a plug-in for Adobe Photoshop for manipulating FITS format images. Also works with Photoshop Elements 2. Includes a short introduction to astronomical image processing.
- Fits4Win2 Viewer (shareware with free beta version) - a FITS viewer for Windows. Works as an extension to Windows Explorer and includes support for viewing thumbnail images of FITS files.
- FitsPlug v2.0 (shareware with free beta version) - a FITS plug-in for Adobe Photoshop for Windows
- FITSview - FITS image viewer from NRAO
- fv - FITS file viewer and editor (supports FITS images and FITS tables)
- GAIA - an image display and analysis tool from the U.K. Starlink Project. It is a derivative of the ESO SkyCat tool
- giv - A cross platform (posix and Windows) image viewer designed especially for scientific vision and computational geometry. Supports interactive brightness and contrast adjustment of 2D images and 3D cubes in various data formats, including FITS. Also supports drawing vector graphics on top of the image.
- GLnemo2 - an interactive 3D visualization program for n-body snapshots which supports 2D and 3D FITS data, as well as other data formats. GLnemo2 is open source, multi-platform (linux, MacosX, windows), and uses qt5 API and openGL hardware acceleration.
- ImageJ - a public domain, Java-based image processing program developed at the National Institutes of Health. ImageJ was designed with an open architecture that provides extensibility via Java plugins and recordable macros. It supports 8-bit and 16-bit integer and 32-bit floating point images and RGB color images.
- ImageTOOLSca (shareware, with a free trial period) - a FITS image viewer for Windows. Supports 16 and 32 bit integer FITS images. It can convert to or from other image formats such as TIFF, JPG, BMP, and Photoshop PSD, and can create AVI animations from a sequence of images. Also supports some image processing tasks such as bias subtraction and flatfielding.
- Libvips - a fully demand-driven, threaded image processing library with no image size limits and with good support for colour. Reads and writes FITS images, as well as TIFF, JPEG, PPM, PNG, and other file formats. Has interfaces to C, C++ and Python, and a command-line interface that can be called from shell scripts.
- MicroObservatory Image 2.0 - astronomical image display program works with FITS and GIF images on PCs and Macs. Can also perform mathematical image processing operations on multiple images.
- PhAst - A flexible IDL tool to display and analyze FITS images. It can calibrate raw images, provide astrometric solutions, and do circular aperture photometry. PhAst allows the user to load, process, and blink any number of images. Requires either an IDL license, or installation of the (free) IDL Virtual Machine.
- QFitsView - An image viewer for 1-D, 2-D, and 3_D FITS images. It is written in C++ and uses the Qt widget library. Binary executables for Microsoft Windows, Linux, and Mac OSX, as well as the source code, are available.
- SkyCat - ESO tool combines image visualization and access to catalogs
- Tria - an advanced image processing suite for Windows platforms (only), including deconvolution, image registration, and noise filtering functions. Supports FITS, TIFF, BMP, JPEG, PNG, and WMF image formats.
- xv (shareware) - interactive image manipulation program for X Window systems
- xINDI - xINDI is a suite of native astronomical software tools for MacOS X built around INDI standard. It consists of binary INDI distribution wrapped into INDI Server application, INDI Control Panel application and FITS Viewer. The viewer is based on CFITSIO library and supports all standard monochromatic and color FITS image formats. It shows both an image (zoomed and stretched automatically, but manual correction of black and white point is available) and the image metadata.
Image Format Converters - FITS to/from GIF, JPEG, etc
- Netpbm - a package of graphics programs and programming library. The documentation is on-line. In particular, see the fitstopmn and pmntofits programs. To first order, the following command converts a jpeg image to a FITS image on most Linux systems:
djpeg file.jpg | pnmtofits > file.fitswhere "djpeg" is available in the libjpeg RPM package.
- ImageMagick - read, write, and manipulate images in over 68 formats
- pbmplus - image file format conversion package
- gimp - GNU Image Manipulation Package
- FITS2jpeg - a FITS to jpeg converter provided by Bill Cotton (NRAO). It needs the CFITSIO and libjpeg libraries and produces grayscale images.
- SAOImage ds9 - this FITS visualization application from SAO allows the image to be saved as a jpeg, tiff, png, or ppm file on disk (use File->Save as->Image...). This currently requires Ghostscript version 6.5 or higher in the path. From there one can go to gif format using xv. Another option to is save the image as Postscript (File->Print...->File...) and then use Ghostscript to convert to gif. (Provided gs was build with a corresponding gif driver included). The ds9 operations can be built into a script using the XPA mechanism.
As an example, the following command will open the file "name.fits", zoom it to fit the window, save it in JPEG format to the file "filename.jpeg", and then exit
ds9 name.fits -zoom to fit -saveimage jpeg filename.jpeg -exit
Other output image formats, besides jpeg, are png, tiff, ppm, and mpeg. Optionally, one can add "-zscale" or "-geometry 800x800" options to customize the output image. These options and more are described using "ds9 --help".
- MicroObservatory Image 2.0 - Image display and processing program can perform FITS to GIF conversion and create RGB color images or animated GIF files.
- fts2gif - a simple FITS to gif converter written by Michal Szymanski (Warsaw University Observatory). It requires the "raw2gif" application from the giflib-3.0 library (Linux and Solaris versions of raw2gif are included in the fts2gif tar file).
- ImageTOOLSca - (shareware, with a free trial period) converts 16 and 32 bit integer FITS images to or from other formats such as TIFF, JPG, BMP, and Photoshop PSD, and can create AVI animations from a sequence of images.
- VOConvert - a tool for converting ASCII or FITS tables to VOTable format. This tool was developed as part of the Virtual Observatory India initiative.
Notes Regarding the Display of FITS Images
An application intended to render a FITS image for viewing by a user has significantly more responsibility than an application intended to handle other standard image formats (e.g., "jpg" or "gif" images). FITS data arrays contain elements which typically represent the values of a physical quantity at some coordinate location. Consequently they need not contain any pixel rendering information in the form of transfer functions, and there is no mechanism for color look-up tables. An application should provide this functionality, either statically using a more or less sophisticated algorithm, or interactively allowing a user various degrees of choice. (See also, a short introduction to astronomical image processing).
Furthermore, the elements in a FITS data array may be integers or floating point numbers. The dynamic range of the data array values may exceed that of the display medium and the eye, and their distribution may be highly nonuniform. Logarithmic, square-root, and quadratic transfer functions along with histogram equalization techniques have proved helpful for rendering FITS data arrays. Some elements of the array may have values which indicate that their data are undefined or invalid; these should be rendered distinctly.
The data array in a FITS image must have a dimensionality between 1 and 999, the boundaries inclusive, indicated by the NAXIS keyword. The extent of any coordinate axis in a FITS data array may, however, consist of only a single element. Hence an algorithm designed to render two-dimensional images will be capable of displaying a three- or four-dimensional FITS array when one or two of the axes consist of a single pixel.
Three-dimensional data arrays (NAXIS=3 with multiple elements along each) are of special interest. Inspection of the World Coordinate System (WCS) keywords in an image with NAXIS = 3 or more may indicate that one of the axes is temporal. Writers of viewer applications should consider presenting such an image in a fashion akin to that used for an animated GIF. Even in the absence of WCS indication of a temporal axis this time-lapse display technique can be effective, and application writers should consider offering it for all three-dimensional arrays.
A FITS image with NAXIS=1 is a one-dimensional entity such as a spectrum or a time series. Writers of applications intended to handle these one-dimensional FITS images should consider presenting such an image as a graphical plot rather than as a two-dimensional picture with a single row.
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Last revised: Tuesday, 10-Nov-2015 15:28:09 EST
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