fits2comp 0.0.1

Create composite color images from FITS files

fits2comp

fits2comp creates composite color images from FITS files using the algorithm of Lupton et al. (2004). Though the algorithm has been implemented in Astropy since I wrote the first version of this program, the main benefit of fits2comp is that you can call it with a number of options that will take care of a number of things for you -- no need to code things up.

You will need to create FITS images in up to three filters by yourself. The FITS images need to be on the same grid and are combined pixel by pixel, WCS information is ignored for this purpose. The WCS of the red channel is used for more advanced functionality: drawing a ruler and a compass, and marking source positions from a file readable as an Astropy table. For my own science with the MUSE integral-field spectrograph, I use the exp_combine recipe or the command muse_cube_filter to create images in several filters from a data cube.

fits2comp is a Python 3 package, installable via pip install fits2comp. It requires Astropy, NumPy, and Pillow-PIL, which will be automatically installed. It uses argparse, so it accepts the --help option. The most important options are -c|--cutoff and -s|--softening, which together set the color scale of the output image. You will have to try a few values to get an image that you like.

Pre-released versions of this package were used to create the images in Zoutendijk et al. (2020, Fig. 1; 2021a, Fig. 1; 2021b, Fig. 1) As an example, I created the Antlia B image in Zoutendijk et al. (2021b, Fig. 1) with

fits2comp \
    --cutoff 10 --softening 1 \
    --ruler "30 arcsec" "196 pc" --name "Ant B" --compass \
    --source-list AntB.csv --offset 5 5 \
    AntB_im/DATACUBE_exp_combine-nomask-noautocal_SDSS_i.fits \
    AntB_im/DATACUBE_exp_combine-nomask-noautocal_SDSS_r.fits \
    AntB_im/DATACUBE_exp_combine-nomask-noautocal_SDSS_g.fits \
    AntB_gri.png

You can find the options used to create a composite image in the image metadata, in case you forget what options you used after painstakingly finding the optimal combination for your target.

Contact

In case of bugs or questions, please file an issue on GitHub or send me an e-mail: [e-mail].

License

This project is licensed under the terms of the MIT License.