Just a few quick words regarding an issue I encountered with RawTherapee recently and struggled to solve, where RawTherapee would not launch.

For my move to Linux Ubuntu, I’m still developing a workflow and identifying which software I will use.  For RAW editing, it’s between Darktable and RawTherapee.  Darktable had the edge for a while, but I’ve just found out that RawTherapee includes native film emulations via HaldCLUT, which is apparently a well-done set of reference files that can be added to the program and used to create a wide range of accurate film emulations.

It’s a relatively minor feature, but one that I want, since I use the VSCO film presets in Adobe Camera Raw currently, and had yet to find a Linux version that worked on RAW files.  So I downloaded and added the HaldCLUT folder to my Home directory, and everything went to hell.

RawTherapee would no longer launch: clicking the icon would cause it to flash for several seconds and then disappear, and running it from the command line got a long series of errors, followed by termination.

The first series of errors referenced the failure of the GTK engine to find the theme “clearlooks.”  Specifically, 21 instances of:

GTK-WARNING **: Unable to locate theme engine in module_path: "clearlooks",

I’m a little fuzzy on this, but believe it has something to do with the move from GTK2 to GTK3 in Ubuntu 16.  At any rate, I used Synaptic Package Manager to search and install the GTK2 engine and dependencies.  It seemed to work, as those lines in the terminal error code went away after that.  (I could be completely wrong about this part and the whole issue could be solved by the second part of my solution, below.  But I don’t know.)

But RawTherapee still wouldn’t launch, and now gave just the following error (which had previously displayed below all the GTK error lines):

terminate called after throwing an instance of 'Glib::FileError'
 Aborted (core dumped)

Not a lot to go on, there.  It took a lot of digging, and several futile uninstall/reinstall cycles, before I finally found a solution, thanks to a hint in a tangential bug report from an OSX user.

As I was starting to suspect, the HaldCLUT folder was somehow to blame (not sure how, but adding it as the only thing that had changed.  However, removing it wouldn’t fix anything without changing the “options” file).

The solution: RawTherapee’s “options” file is bad and needs to be renamed/deleted.  It’s located at: Home –> .config –> RawTherapee.  (.config is a hidden file, you’ll need to Ctrl-H to be able to see them.)

Delete (or rename, if you’re cautious) the “options” file and then launch RawTherapee.  It will create a new “options” file and should open successfully.  Once it’s open, immediately open the preferences and, on the “Image Processing” tab, near the bottom, tell it where to find the HaldCLUT folder.

Tell it EXACTLY, as in use the file manager window that will appear to select the specific HaldCLUT file – selecting the parent directory to wherever you placed it will NOT work.

Save the preferences by clicking OK then close the program.  Relaunch RawTherapee and it should be fixed and successfully open, and when you go to the Film Emulations tab, all the various emulations will be available.

I spent several hours tracking this down and fixing it – and while this post is somewhat off-topic for my usual readership, I’m putting it up here in hopes that it will help save someone else a lot of trouble!


Brent Pennington is a freelance photographer and the driving force behind The Roving Photographer. When he\’s not working with portraiture or promotional clients, he’s usually in the field, hiking, or kayaking in pursuit of nature and wildlife shots.

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