# Getting Started¶

Tutorial:

For ease of use we also provide with the package, a commandline python script to run the code, imganalysis.py.

imganalysis can be used in the commandline by running:

python imganalysis.py


The script has several possible options:

-h, --help

show this help message and exit.

-A

Calculate asymmetry parameter.

-As

Calculate shape asymmetry parameter.

-Aall

Calculate all asymmetries parameters.

-sersic, --sersic

Calculate Sersic profile.

-spm, --savepixmap

Save calculated binary pixelmaps.

-sci, --savecleanimg

Save cleaned image.

-li, --largeimage

Use large cutout for sky background estimation.

-lif, --largeimagefactor

Factor to scale cutout image size (–imgsize) so that a better background value can be estimated.

-f FILE, --file FILE

File which contains list of images, and RA DECS of object in image.

-fo FOLDER, –folder FOLDER

Give location for where to save output files/images

-src {SDSS,LSST}, –imgsource {SDSS,LSST}

Telescope source of the image. Default is SDSS. This option specifies method of ingestion of the FITS image files.

-s IMGSIZE, --imgsize IMGSIZE

Size of image cutout to analyse.

-cc CATALOGUE, –catalogue CATALOGUE

Check if any object in the provided catalogue occludes the analysed object.

-ns NUMSIG, –numsig NUMSIG

Radial extent to which mask out stars if a catalogue is provided.

-fs {1,3,5,7,9,11,13,15}, –filtersize {1,3,5,7,9,11,13,15}

Size of kernel for mean filter.

-par {multi,parsl,none}, –parlib {multi,parsl,none}

Choose which library to use to parallelise script. Default is none.

-n CORES, --cores CORES

Number of cores/process to use in calculation

If this option is provided then the script expects there to be precomputed masks in the format pixelmap_ + filename in the same folder as the images for analysis

-cas, --cas

If this option is enabled, the CAS parameters are calculated (Gini, M20, r20, r80, concentation, smoothness)

Example:

python imganalysis.py -f images.csv -fo output/ -Aall -spm -sci -src sdss -sersic -cas -n 4


The above command will run the code over all the images in the file images.csv, and calculate all the asymmetry statistics, alongside the CAS and Sersic statistics. This will generate a folder output where pixelmaps of the object, cleaned images, and calculated parameters (parameters.csv) are stored. The command will also run the code in parallel over 4 processors. The input csv file (images.csv in this example) should have the following columns: filename, ra, dec The filename column should contain the path to the image relative to the directory you are runnning the script in. RA, and DEC shoul be the location of the galaxy/object to be analysed.

If imganalysis.py is run with the -spm and -sci options, then it will automatically plot the various outputs using matplotlib at the end of a run. This can be useful to asses by eye the various setting used in that run for generating the segmentation map, and size of star to mask out.

imganalysis.py is provided as an easy option for calculating various morphology statistics. However, the package can also be used as a general purpose library for building your own scripts. The package publicly exposes several of the functions in order to achieve this.