Ginga: an open-source astronomical image viewer and toolkit

Ginga is a new astronomical image viewer written in Python. It uses and inter-operates with several key scientific Python packages: NumPy, Astropy, and SciPy. A key differentiator for this image viewer, compared to older- generation FITS viewers, is that all the key components are written as Python classes, allowing for the first time a powerful FITS image display widget to be directly embedded in, and tightly coupled with, Python code. We call Ginga a toolkit for programming FITS viewers because it includes a choice of base classes for programming custom viewers for two different modern widget sets: Gtk and Qt, available on the three common desktop platforms. In addition, a reference viewer is included with the source code based on a plugin architecture in which the viewer can be extended with plugins scripted in Python. The code is released under a BSD license similar to other major Python packages and is available on GitHub. Ginga has been introduced only recently as a tool to the astronomical community, but since SciPy has a developer focus this talk concentrates on programming with the Ginga toolkit. We cover two cases: using the bare image widget to build custom viewers and writing plugins for the existing full-featured Ginga viewer. The talk may be of interest to anyone developing code in Python needing to display scientific image (CCD or CMOS) data and astronomers interested in Python-based quick look and analysis tools.