ds9

Context: concept

Synopsis

SAOImageDS9 is the de facto standard astronomical image display application.

Description

SAOImageDS9 (DS9) is an astronomical imaging and data visualization application. DS9 supports FITS images and binary tables, multiple frame buffers, region manipulation, and many scale algorithms and colormaps. It provides for easy communication with external analysis tasks and is highly configurable and extensible via XPA and SAMP. DS9 is a stand-alone application. It requires no installation or support files. All versions and platforms support a consistent set of GUI and functional capabilities. DS9 supports advanced features such as 2-D, 3-D, and RGB frame buffers, mosaic images, tiling, blinking, geometric markers, colormap manipulation, scaling, arbitrary zoom, cropping, rotation, pan, and a variety of coordinate systems. The GUI for DS9 is user-configurable. GUI elements such as the coordinate display, panner, magnifier, horizontal and vertical graphs, button bar, and color bar can be configured via menus or the command line.

DS9 Features and Capabilities

DS9 is far more than just a simple FITS display tool. Some highlights include:

Supports FITS images, binary tables (event files), multi-dimensional data cubes, multi-extension files, compressed images, all-sky Healpix images, mosaics, raw data arrays, bitmap images (png, jpeg, tiff, gif).
Supports multiple frames, n-D slices, 3D rendering of data cubes, Red Green Blue (RGB) "true" color frames, Hue Saturation Value (HSV) or Hue Lightness Saturation (HLS), tiling, blinking, and fading frames. Multiple frames can be matched to the same coordinate system, colormaps, scaling, and more.
Outputs can be printed to PostScript or saved to various bitmap formats. Supports creating animations based on multiple frames, slices through n-D data cubes, or 3D rendering.
Region (markers) include circle, ellipse, polygon, box, points with styling options (color, fill, line thickness, labels, fonts). Regions can be combined together (composite) and can be grouped and given identifying labels (tags). Easily create grids of shapes (annuli and various "panda" shapes (Pie AND Annulus)). Regions can be read from and written in various formats including DS9 format, CIAO, IRAF, and VOTable.
Supports arbitrary zoom, pan, rotate, and cropping of the display. Tables are binned into images with arbitrary binning and filtering applied. Images can further be blocked.
Pixel values can be scaled to accentuate features using linear, log, square root, exponential (power), and arc hyperbolic sine functions. Scaling limits can be set manually or using various percentile ranges.
Scaled pixel values are mapped to colors in the built-in colormaps. These include the standard DS9 colormaps, the Matplotlib colormaps, a set of cube-helix colormaps, and many more.
Supports all standard FITS World Coordinate Systems (WCS), as well as those used by legacy packages IRAF and AIPS. Supports multiple coordinate systems. Fully customizable coordinate display settings.
Built-in 2D plotting of histograms, scatter, and line plots.
Prism: the integrated table display widget.
Write analysis notes on the built-in notepad widget.
Backup and restore functionality.
Create and display contours on images. Easily copy contours from one frame onto another.
Allows for translucent mask layers.
Users can set preferences for all menu options.
Fully scriptable using XPA or SAMP.
Rich catalog support includes accessing catalogs using Virtual Observatory protocols, importing catalogs from FITS tables or comma-separated value (CSV) ASCII files. Plotting catalog properties. Linked views, where selecting a catalog row will highlight the catalog marker in the image display and any plots; similarly, selecting in the plot or image will highlight the corresponding catalog row. Programmable catalog markers (e.g., plot variable sources in red).
Access to several image servers removes barriers to multi-wavelength analysis.
Illustrate mode allows users to include images and other static display elements to prepare images for publication.
and much more...

For more information see the DS9 Reference Manual and the exhaustive SAOImageDS9 Interface and Internal Design document.

DS9 in CIAO

DS9 is, by default, included with CIAO. It is one of the few astronomical imaging applications that can directly display Chandra FITS event files (binary tables). CIAO provides a thin wrapper shell script around the DS9 command that is used to automatically load DAX , CIAO's DS9 analysis extensions. CIAO provides a port of DS9 that is expected to be compatible with most operating system versions for a particular set of hardware (i.e., Linux, macOS ARM, or macOS Intel).

Examples

Example 1

unix% ds9

Simply running the command "ds9" will launch the application.

Example 2

unix% ds9 image.fits

This command launches the DS9 application and will load the file named "image.fits".

Example 3

unix% ds9 image.fits acis_evt.fits

This example loads multiple (2) files into separate frames. The first frame will be an image, the second frame is an ACIS event table that DS9 will automatically bin into an image for display.

Example 4

unix% ds9 image.fits -log -cmap bb -scale limits 0 100 -zoom to 3 -pan
to 512 512 physical

This example shows some of the command line options . The command line options are processed in order going from left to right. First, the pixel value scaling function is set to log scale. Then the colormap is set to DS9's "bb" colormap. The pixel scaling range is set from 0 to 100. Pixels are zoomed to 3 and the display is panned (re-centered) to pixels (512, 512) in the physical coordinate system.

About

DS9 is a Tcl/Tk application. The GUI is implemented as a very thin layer of Tk. A number of Tk Canvas widgets were created in C++ to support all the functionality needed. Basically, all the real work is done in C++. DS9 inherited SAOTNG's support of regions, XPA, external analysis support, and the general GUI. However, all the visualization techniques come directly from SAOImage.

The current version of DS9 is composed of the Tk widgets created along with support from about 20 other open source products. The distributed binaries consist of a self-contained, self-extracting archive and application, which provides an independent Tcl/Tk environment without requiring installation.