I saw that is a very common error but I looked for a lot to solve it and nothing worked.
All work fine with the last version of Omeka classic that I installed on OVH but there is no thumbnails: when I try to add a path in settings it’s written “The ImageMagick directory path does not work.”. I tried a lot of things like “usr/bin”, “usr/locale/bin”, I tried to change the config.ini too but no success. I am sure thaht ImageMagick is installed on my server but do you have any idea to have the path (no answer in OVH forums)? I tried Omeka S too, I prefer Omeka classic for some reasons but it seems that ImageMagick works with Omeka S… so if someone could help me it would be very kind because I spent a lot of time on this error!
I finally found the problem, hope this will help someone with the same problem:
in your application/config/config.ini file, change
fileDerivatives.strategy = “Omeka_File_Derivative_Strategy_ExternalImageMagick” by
fileDerivatives.strategy = “Omeka_File_Derivative_Strategy_GD” removing the semicolon.
GD supports fewer kinds of images and files, and it additionally lacks some other features… it’s widely available though so it can be a good choice on servers that are problematic for whatever reason.
In general running a command like which convert when connecting to your server by SSH will tell you where ImageMagick is installed, but servers can do things like disable command execution and a few other settings that make it so Omeka can’t find or run ImageMagick.
Some servers have the “imagick” PHP extension installed; if this is the case, you can use the Imagick strategy and get all the features of ImageMagick without needing to mess with the command line.