There are a couple of other methods to open RAW files in GIMP, but those two programs are the best free options available. You can apply any non-destructive adjustments you want, and then it passes the processed RAW file directly back into GIMP for additional editing and closes itself. Once you’ve got an appropriate processor installed, opening a RAW file in GIMP will automatically launch it as a plugin. They can both open any RAW files produced by a modern camera, and they integrate seamlessly and instantly with GIMP.

The two leading options are darktable and RawTherapee. You’ll need to install a secondary program to handle your RAW files called a RAW processor. GIMP doesn’t know how to open RAW files by default, but there are a few different ways to get around this problem. For example, Nikon cameras use the NEF format.

Then you can create a launcher to run gimp like this in the future.Modern cameras use RAW formats to get the best possible image quality, and most camera manufacturers use their own unique proprietary version of a RAW file. This command simply specifies a particular theme ( gtkrc) to use with a gtk application, it will NOT affect your general Ubuntu theme or interfere with any other programs. Then, to test it with gimp (substituting gimp-2.6 for your version), run: GTK2_RC_FILES=$HOME/.themes/Darkilouche/gtk-2.0/gtkrc gimp-2.6 Just unpack the zip and create a new folder called Darkilouche and place in it the contents of the zip (folders labelled gtk-2.0. It was created by a while ago here and the version you want is 0.2.3, available here as well. (It will work until gimp switches to gtk3 around the time of gimp 3.) It may not be quite as dark as the one you have in mind, but it's good and you may be able to modify it further. There is one gtk2 theme that I use for gimp 2.6, although it should work for gimp 2.8, and that is Darkilouche.

How to use darktable with gimp