  We describe Ganalyzer, a model-based tool that can automatically analyze and
classify galaxy images. Ganalyzer works by separating the galaxy pixels from
the background pixels, finding the center and radius of the galaxy, generating
the radial intensity plot, and then computing the slopes of the peaks detected
in the radial intensity plot to measure the spirality of the galaxy and
determine its morphological class. Unlike algorithms that are based on machine
learning, Ganalyzer is based on measuring the spirality of the galaxy, a task
that is difficult to perform manually, and in many cases can provide a more
accurate analysis compared to manual observation. Ganalyzer is simple to use,
and can be easily embedded into other image analysis applications. Another
advantage is its speed, which allows it to analyze ~10,000,000 galaxy images in
five days using a standard modern desktop computer. These capabilities can make
Ganalyzer a useful tool in analyzing large datasets of galaxy images collected
by autonomous sky surveys such as SDSS, LSST or DES. The software is available
for free download at http://vfacstaff.ltu.edu/lshamir/downloads/ganalyzer, and
the data used in the experiment are available at
http://vfacstaff.ltu.edu/lshamir/downloads/ganalyzer/GalaxyImages.zip.
