# Converting to RGB

If you have two or more images of the same scene taken at different wavelengths, you may wish to combine them to create a colour composite.

For ultimate control, you can do this manually using imview. Simply map your channels to RGB values using imview and then sum the results.

For convenience, AstroImages.jl provides the function composecolors.

## Using composecolors

We'll demonstrate composecolors using Hubble images of the Antenae colliding galaxies.

One can be very scientific about this process, but often the goal of producing color composites is aesthetic or about highlighting certain features for public consumption.

I'll set the default color map to grayscale to avoid confusion.

using AstroImages

AstroImages.set_cmap!(nothing)

Let's start by downloading the separate color channel FITS files:

antred = AstroImage(download("http://www.astro.uvic.ca/~wthompson/astroimages/fits/antenae/red.fits"))
antgreen = AstroImage(download("http://www.astro.uvic.ca/~wthompson/astroimages/fits/antenae/green.fits"))
antblue = AstroImage(download("http://www.astro.uvic.ca/~wthompson/astroimages/fits/antenae/blue.fits"))