Install vncsnapshot by entering the following commands in the terminal:
sudo apt update sudo apt install vncsnapshot
Description:
A utility that takes JPEG snapshots from VNC servers
VNC Snapshot is a command-line program for VNC. It will save a JPEG image of the VNC server's screen. . To use this you must be able to connect directly to the VNC server via a TCP connection. It does not yet work for connections tunnelled over SSH.
Homepage: http://vncsnapshot.sourceforge.net/
Version: 1.2a-5.1build1
Section: universe/x11