ExFITS

ExFITS provides Elixir bindings to the CFITSIO library for working with FITS (Flexible Image Transport System) files, commonly used in astronomy and scientific data processing.

Features

• Read and write FITS files
• Support for various data types (float, integer, short, etc.)
• Read and write header cards
• Helper functions for common FITS operations
• Optional integration with Nx tensors for numerical computing

Installation

If available in Hex, the package can be installed by adding exfits to your list of dependencies in mix.exs:

def deps do
  [
    {:exfits, "~> 0.2.0"},
    {:nx, "~> 0.6.2"}  # Optional, for tensor functionality
  ]
end

CFITSIO Dependency

This library uses the CFITSIO C library via Elixir NIFs. You must have CFITSIO installed on your system. CFITSIO may also be installed from source by running mix compile.nif

Install CFITSIO (macOS)

brew install cfitsio

Or build from source:

git clone https://github.com/HEASARC/cfitsio.git
cd cfitsio
./configure
make
sudo make install

Build NIF

The NIF will be built automatically when you run:

mix compile

If you encounter build errors, ensure cfitsio is installed and available to your compiler/linker.

Usage Examples

Writing a Simple FITS File

# Create a simple 10x10 float image with values 1.0 to 100.0
data = for y <- 1..10, x <- 1..10, do: (y - 1) * 10 + x
bin_data = :binary.list_to_bin(for val <- data, do: <<val::float-32>>)

# Generate basic FITS headers
headers = [
  "SIMPLE  =                    T / Standard FITS format",
  "BITPIX  =                  -32 / IEEE single precision floating point",
  "NAXIS   =                    2 / Number of axes",
  "NAXIS1  =                   10 / Size of axis 1",
  "NAXIS2  =                   10 / Size of axis 2", 
  "ORIGIN  = &#39;Elixir ExFITS&#39;     / File origin",
  "END"
]

# Write the FITS file
{:ok, filename} = ExFITS.write_fits("output.fits", bin_data, headers)

Working with Nx Tensors

If you have the Nx package installed, you can easily work with FITS data as tensors:

# Read a FITS file directly into an Nx tensor
{:ok, tensor} = ExFITS.to_nx("image.fits")

# Perform tensor operations
processed_tensor = Nx.multiply(tensor, 2.0)

# Write the tensor back to a FITS file
ExFITS.write_nx(processed_tensor, "processed_image.fits")

Documentation

Documentation can be generated with ExDoc:

License

ExFITS is released under the MIT License. See the LICENSE file for details.