Script for Plasma 5 which takes screenshot, when you lock screen, blures it and makes it the lockscreen background.
Dependencies: scrot, imagemagic
1. Locate your kscreenlocker_greet file .(mine is /usr/lib/kscreenlocker_greet).
2. Rename it to kscreenlocker_greet-original.
3. Create kscreenlocker_greet file with following content: (Your path of background.png can differ, so find it and replace the path if needed)
scrot -z /tmp/s.png
convert /tmp/s.png -channel RGB -blur 0x4 /usr/share/plasma/look-and-feel/org.kde.breeze.desktop/contents/components/artwork/background.png
4. chmod +x kscreenlocker_greet
5. chmod 777 /usr/share/plasma/look-and-feel/org.kde.breeze.desktop/contents/components/artwork/background.png