how to take screenshots using keyboard combo in Kubuntu 16.04.3?

Taking a picture of the desktop using keyboard shortcut and the image is automatically saved to the user desktop

Using Spectacle - KDE Framework 5 default screenshot capture utility:

$ spectacle --help
Usage: spectacle [options]
KDE Screenshot Utility

Options:
  -v, --version              Displays version information.
  -h, --help                 Displays this help.
  --author                   Show author information.
  --license                  Show license information.
  --desktopfile <file name>  The base file name of the desktop entry for this
                             application.
  -f, --fullscreen           Capture the entire desktop (default)
  -m, --current              Capture the current monitor
  -a, --activewindow         Capture the active window
  -u, --windowundercursor    Capture the window currently under the cursor,
                             including parents of pop-up menus
  -t, --transientonly        Capture the window currently under the cursor,
                             excluding parents of pop-up menus
  -r, --region               Capture a rectangular region of the screen
  -g, --gui                  Start in GUI mode (default)
  -b, --background           Take a screenshot and exit without showing the GUI
  -s, --dbus                 Start in DBus-Activation mode
  -n, --nonotify             In background mode, do not pop up a notification
                             when the screenshot is taken
  -o, --output <fileName>    In background mode, save image to specified file
  -d, --delay <delayMsec>    In background mode, delay before taking the shot
                             (in milliseconds)
  -w, --onclick              Wait for a click before taking screenshot.
                             Invalidates delay

Command:

spectacle -f -b -n -o "$HOME/Desktop/ScreenShot-$(date +%Y%m%d%H%M%S).jpg"

will capture the entire desktop image to the user Desktop folder aka desktop.

The command can be added to the KDE menu with the KDE menu editor: https://docs.kde.org/stable5/en/kde-workspace/kmenuedit/index.html

The command can be launched with the user defined shortcut:

When the shortcut is clicked the picture is saved to the desktop:

ksnapshot is the KDE (kubuntu) version of screen capture. It can be launched from the menu or by pressing prt scrn button