The interface is inspired by Erin Sheldon’s fitsio Python package.
On linux or OS X, if it isn’t already installed on your system, the cfitsio library is automatically downloaded and compiled (in your Julia packages directory). On Windows, a compiled dll will be downloaded.
Open an existing file for reading:
julia> using FITSIO julia> f = FITS("file.fits") file: file.fits mode: r extnum exttype extname 1 image_hdu 2 binary_table
(At the REPL, information about the file contents is shown.)
A FITS file consists of one or more header-data units (HDUs), concatenated one
after the other. The
FITS object therefore is represented as a collection
of these HDUs.
Get information about the first HDU:
julia> f # get the first extension file: file.fits extension: 1 type: IMAGE image info: bitpix: -64 size: (800,800)
Iterate over HDUs in the file:
julia> for hdu in f; println(typeof(hdu)); end ImageHDU TableHDU
Each HDU can contain image data, or table data (either binary or ASCII-formatted). For image extensions, get the size of the image without reading it:
julia> ndims(f) 2 julia> size(f) (800,800) julia> size(f, 2) 800
Read an image from disk:
julia> data = read(f); # read an image from disk julia> data = read(f, :, 790:end); # read just a subset of image
Show info about a binary table:
julia> f file: file.fits extension: 2 type: BINARY TABLE rows: 20 columns: col2 (5A) col1 (1K)
Read a column from the table:
julia> data = read(f, "col1")
Read the entire header into memory and get values from it:
julia> header = read_header(f); # read the entire header from disk julia> length(header) # total number of records in header 17 julia> haskey(header, "NAXIS1") # check if a key exists true julia> header["NAXIS1"] # get value by keyword 800 julia> header # get value by position 800 julia> get_comment(header, "NAXIS") # get comment for a given keyword "length of data axis 1"
Read just a single header record without reading the entire header:
julia> read_key(f, 4) # by position ("NAXIS1",800,"length of data axis 1") julia> read_key(f, "NAXIS1") # read by keyword (800,"length of data axis 1")
Manipulate a header in memory:
julia> header["NEWKEY"] = 10 # change or add a keyword julia> set_comment!(header, "NEWKEY", "this is a comment")
Close the file:
FITS objects are also closed automatically when garbage collected.)
Open a new file for writing:
julia> f = FITS("newfile.fits", "w");
The second argument can be
"r" (read-only; default),
"w" (write). In “write” mode, any existing file of
the same name is overwritten.
Write an image to the file:
julia> data = reshape([1:100], 5, 20); julia> write(f, data) # Write a new image extension with the data
To write some header keywords in the new extension, pass a
FITSHeader instance as a keyword:
Write a table to the file:
julia> data = ["col1"=>[1., 2., 3.], "col2"=>[1, 2, 3]]; julia> write(f, data) # write a new binary table to a new extension