update-desktop-database ~/.local/share/applications

# Open all images with imv
xdg-mime default imv.desktop image/png
xdg-mime default imv.desktop image/jpeg
xdg-mime default imv.desktop image/gif
xdg-mime default imv.desktop image/webp
xdg-mime default imv.desktop image/bmp
xdg-mime default imv.desktop image/tiff

# Open PDFs with the Document Viewer
xdg-mime default org.gnome.Evince.desktop application/pdf