Snipping in Lubuntu

One feature that I find very useful in Windows 10 is the Snipping Tool.   The Snipping Tool is mapped to Win-Shift-s key combination.   After pressing that meta-key combination, the screen grays out, and you can select an area of the screen to copy to the system clipboard.    This is really useful for splatting images quickly into an email (or other document) with a minimum of effort.   Print Screen and Alt-Print Screen were useful for grabbing images of a whole screen or of a whole window.   But many times we only want a small portion of the screen, and the Snipping Tool is a useful way to grab exactly what you need.

In my last post, my old laptop got a second lease on life with a Lubuntu installation and an upgrade to 2GB of memory.  I am spoiled  by the Snipping Tool on my Windows 10 computers, so I'm looking for a way to get that functionality with Lubuntu.

As with many things in life, "da google" is your friend.   Googling "screen capture" or "screen image" returns lots of hits showing screen images from Lubuntu, but not a lot of information describing how to grab that screen image.    Eventually, I found some information about a screen capture utility called scrot (short for SCReen shOT).  In this post, I'll discuss using scrot and mtpaint to add Snipping Tool functionality to Lubuntu.  Mtpaint is installed as part of the Lubuntu distribution, but you may need to install scrot  yourself. Finally we'll map them to meta-keys in the Openbox window manager.

First, make sure scrot and mtpaint are installed on your system.     Open a terminal window, and try executing scrot -v.  If the tool loads and displays a version number, everything is good.   If it doesn't load, you'll see a message like:

The program 'scrot' is currently not installed. You can install it by typing: 
sudo apt install scrot 

If you get that message, go ahead and install the tool using apt:

sudo apt install scrot

Now you should have both tools installed.  I'll start by running them from the command line.  First, try
scrot --select

You'll notice that your terminal window pauses, waiting for you do do something.  With your mouse, click and drag over any section of your screen, creating a rectangle.  Release the mouse button, then in your terminal window type
ls -l *png

and your output will look something like the following.   Scrot creates files with the datetime and images size in the filename:

tom@dv8000:~$ ls -l *png
-rw-rw-r-- 1 tom tom 131103 Jan 13 11:48 2018-01-13-114835_1440x875_scrot.png
-rw-rw-r-- 1 tom tom    510 Jan 13 11:48 2018-01-13-114856_184x172_scrot.png
tom@dv8000:~$

Our next step is to get the the output into mtpaint.  Scrot has a couple of options to facilitate sending the captured image to another program.   The -exec option tells scrot to run another program, and the $f will pass the name of the saved file.   Try the next command; scrot will save the output in /tmp/ScrotSave.png and then execute mtpaint with that filename as the argument.

scrot --select --exec 'mtpaint $f ' /tmp/ScrotSave.png

Now we have all the facilities of mtpaint at our disposal to edit the image.  Using mtpaint, we can save that image back to disk, or just copy it to the system clipboard  using Ctrl-C, then Edit -> Export Clipboard to System from the drop-down menu.

Finally, we'll map this command to a meta-key combination in Lubuntu's openbox window manager.   From your home directory, navigate to the .config directory, then to the openbox directory, and look for the XML configuration file.   In my system, it's lbubuntu-rc.xml:

tom@dv8000:~$ cd .config 
tom@dv8000:~/.config$ cd openbox  
tom@dv8000:~/.config/openbox$ ls -l 
total 36 
-rw-r--r-- 1 tom tom 33422 Jan 13 15:10 lubuntu-rc.xml 
tom@dv8000:~/.config/openbox$ 

There are lots of things that we can configure here, but we're only interested in the keybindings. Before you begin, copy the xml file to a safe place! If you make an error, you don't want to leave the configuration file a mess, and you can restore it using your saved copy.  After creating a backup copy, edit lubuntu-rc.xml with your favorite text editor (leafpad and vi are both installed on Lubuntu, don't use a document editor like Abiword, OpenOffice, or LibreOffice). 

Find the line where the Lubuntu specific keybinding start, and add the XML starting with the <keybind> tag through the closing </keybind> tag:

    382     <!--  Lubuntu specific : Keybindings -->
    383     <!--  Lubuntu specific : Keybindings -->
    384     <!--  Windows-s key to select screen and copy to mtpaint -->
    385     <keybind key="W-s">
    386       <action name="Execute">
    387         <command>  scrot -s -e 'mtpaint $f ' /tmp/ScrotSave.png 
    388      </action>
    389     </keybind>
 

Let's look at what we've done:   Line 384 is a comment describing our change. In line 385, we start a new keybinding, capturing the meta-character combination Windows and the "s" key.  The action will be to Execute the command within the command tags on line 387, which is the scrot command that we executed in the terminal prompt above.

Next, save the file, and refresh the window manager with the new configuration information:

openbox --reconfigure

If all went well, openbox will not display any output.   If there is an error, openbox pops up a message describing the error and its location in the XML file.   After openbox has reloaded the XML file, test your keymap by pressing the Windows and S, then select part of your screen using the mouse.   After you release the mouse key, mtpaint will open with a copy of the image you selected. 

Now you have a quick and easy way to grab a selected part of your screen and manipulate it for further use.  Save the image as a file, or copy it to the system clipboard in mtpaint.

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References:

In addition to the Unix man pages for scrot and mtpaint,  the following web pages should be useful for readers desiring a deeper look into the keybinding and mtpaint.

https://wiki.archlinux.org/index.php/openbox#Keybinds

http://mtpaint.sourceforge.net/handbook/en_GB/chap_04.html#SEC6