Configure a keyboard shortcut in Lubuntu 18.04 to take a screenshot of a screen region

As installed, Lubuntu 18.04 is configured so that the user can capture a screenshot of the whole screen by pressing the PrtScrn key, and a screenshot of the active window by pressing Alt+PrtScrn. However, no keyboard shortcut is configured to enable the user to capture a user-specified region of the screen.

Now, as it happens, the ‘-s‘ option of the scrot command allows a region of the screen to be captured and saved. The man page for scrot tells us:

-s, --select
Interactively select a window or rectangle with the mouse.

So here is how to configure a keyboard shortcut to do that in Lubuntu 18.04.

Open the file ~/.config/openbox/lubuntu-rc.xml in a text editor (either nano from the command line or LXTerminal from the GUI) and look for the following lines:

    <keybind key="Print">
      <action name="Execute">
        <command>lxsession-default screenshot</command>
      </action>
    </keybind>
    <keybind key="A-Print">
      <action name="Execute">
        <command>lxsession-default screenshot window</command>
      </action>
    </keybind>

Append the following lines to that group of lines:

    <keybind key="C-A-Print">
      <action name="Execute">
        <command>scrot -s</command>
      </action>
    </keybind>

The new group of lines should then look like this:

    <keybind key="Print">
      <action name="Execute">
        <command>lxsession-default screenshot</command>
      </action>
    </keybind>
    <keybind key="A-Print">
      <action name="Execute">
        <command>lxsession-default screenshot window</command>
      </action>
    </keybind>
    <keybind key="C-A-Print">
      <action name="Execute">
        <command>scrot -s</command>
      </action>
    </keybind>

Now logout and login again.

If you now press Ctrl+Alt+PrtScrn and use your mouse to select a rectangular region of the screen, a screenshot of that region will be saved automatically to your home directory. Simple.

You just have to remember:

PrtScrn — Captures the entire screen.
Alt+PrtScrn — Captures the active window.
Ctrl+Alt+PrtScrn — Captures the area of the screen you select with the mouse.