| Documentation | Build Status | Code Coverage |
|---|---|---|
 |
 |
 |
AstroImages.jl allows you load and visualize images from a
astronomical FITS files using the
popular Images.jl
and Plots.jl Julia packages.
AstroImages.jl uses FITSIO.jl to
read FITS files.
AstroImages.jl is available for Julia 1.6 and later versions, and can be
installed with Julia built-in package
manager.
pkg> add AstroImagesYou may also need to install ImageIO.jl for images to display in certain environments.
After installing the package, you can start using it with
julia> using AstroImagesImages will automatically display in many environments, including VS Code, Jupyter, and Pluto. If you're using a REPL, you may want to install an external viewer like ImageShow.jl, ElectronDisplay.jl, or ImageInTerminal.jl.
You can load and read the the first extension of a FITS file with the load
function, from FileIO.jl:
julia> load("file.fits")
1300×1200 Array{UInt16,2}:
[...]The second argument of this load method is the number of the extension to
read. Read the third extension of the file with:
julia> load("file.fits", 3)
1300×1200 Array{UInt16,2}:
[...]If unspecified, the first image HDU will be loaded.
The package provides a new type, AstroImage to integrate FITS images with
Julia packages for plotting and image processing. The AstroImage function has
the same syntax as load. This command:
julia> img = AstroImage("file.fits")will read the first valid extension from the file.fits file.
If you are working in a Jupyter notebook, an AstroImage object is
automatically rendered as a PNG image.
AstroImage automatically extracts and store wcs information of images in a NTuple{N, WCSTransform}.
FITS Headers can be accessed directly from an AstroImage:
julia> img["HEAD1"] = 1.0
julia> img["HEAD1",Comment] = "A comment describes the meaning of a header keyword"
julia> img["HEAD1"]
1.0
julia> push!(img, History, "We can record the history of processes applied to this image in header HISTORY entries.")Any AbstractArray (including an AstroImage) can be displayed using imview. This function renders an
arbitrary array into an array of RGBA values using a number of parameters. If the input is an AstroImage{<:Number},
an AstroImage{RGBA} will be returned that retains headers, WCS information, etc.
julia> imview(img; clims=Percent(99.5), cmap=:magma, stretch=identity, contrast=1.0, bias=0.5)Very large Images are automatically downscaled to ensure consistent performance using restrict from Images.jl. This function filters the data before downscaling to prevent aliasing, so it may take a moment for truly huge images. In these cases, a faster method that doesn't prevent aliasing would be imview(img[begin:10:end, begin:10:end]) or similar.
imview is called automatically on AstroImage{<:Number} when using a Julia environment with rich graphical IO capabilities (e.g. VSCode, Jupyter, Pluto, etc.).
The defaults for this case can be modified using AstroImages.set_clims!(...), AstroImages.set_cmap!(...), and AstroImages.set_stretch!(...).
A color composite image (e.g. RGB) can be constructed using the composecolors function.
julia> rgb = composecolors([img1, img2, img3])Where img1, img2, img3 are arrays or AstroImages containing data of red, blue and green channels respectively.
composecolors also supports more complex mappings, for example merging two bands according to color schemes from
ColorSchemes.jl.
See the docs for more information.
An AstroImage object can be plotted with Plots.jl package. Just use
julia> using Plots
julia> implot(img)and the image will be displayed as an image series using your favorite backend. Plotly, PyPlot, and GR backends have been tested.
implot supports all the same syntax as imview in addition to keyword arguments
for controlling axis tick marks, WCS grid lines, and the colorbar.
If your FITS file contains world coordinate system headers, AstroImages.jl can use WCS.jl to convert between pixel and world coordinates. This works even if you have sliced or your image to select a region of interest:
julia> img_slice = img[100:200,100:200]
julia> coords_world = pix_to_world(img_slice, [5,5])
[..., ...]
julia> world_to_pix(img_slice, coords_world)
[5.0,5.0] # approximatelyThe AstroImages.jl package is licensed under the MIT "Expat" License. The
original author is Mosè Giordano.