• I've definitely found a bug (it you're not sure, please use image.sc instead)
• I've checked https://qupath.github.io for a new release that might already have fixed the issue
• I've checked the Changelog to see if the bug has already been fixed in the next release
• I've checked for existing GitHub issues describing the same problem

Bug report

Describe the bug

On Linux, export snapshot commands only works if the extension is specified in the filename and fails silently otherwise.

To Reproduce

Steps to reproduce the behavior:

1. Go to File -> Export snapshots... -> <Any of the 4 commands>
2. If the file format doesn't end with .png, .tif or .jpg a file is saved as expected. If not, no file is saved and running the command fails silently.

Expected behavior

The command should add the extension automatically to save the snapshot. If not possible it should output a warning asking the user to add the desired extension into the filename.
This behavior is different on Windows, where the extension is automatically added to the provided filename.

Desktop (please complete the following information):

• OS: Ubuntu 24.04.2 LTS
• QuPath Version: 0.7.0 (also tested with 0.6.0)

Additional context

On Linux, if the provided name ends with .png, .tif or .jpg, the file will be saved in this format whatever the selected output format in the GUI.