To only shoot the current screen is not the default behaviour, nor is it an option in gnome-screenshot, nor any other screenshot application as far as I know.

Like practically anything however, it can be scripted.

An example

The script further below will:

• take a screenshot


• automatically create a (numbered) image in an arbitrary directory



• automatically crop the image to the section of the screen you are currently on (retrieved from the mouse position), and create a cropped image named:

  
  
  

  cropped_<image>.png
  
  

To prevent overwriting earlier screenshots, these cropped images are numbered like their oroginals.

screenshot

if I am on the left screen:

if I am on the right screen:

The script

#!/usr/bin/env python3

import os

from PIL import Image

import subprocess



# ---set the name of your (automatically numbered) screenshots (no extension)

imagename = "screenshot"

# ---set the path to where you (want to) save your screenshots

savepath = "/home/jacob/Bureaublad"



def get(cmd):

    return subprocess.check_output(cmd).decode("utf-8")



n = 1 

while True:

    name = imagename+"_"+str(n)+".png"

    path = os.path.join(savepath, name)

    if os.path.exists(path):

        n += 1

    else:

        break



# make the shot

subprocess.call(["gnome-screenshot", "-f", path])

# get the width of the left screen

screenborder = [int(n) for n in [s for s in get("xrandr").split()

                if "+0+0" in s][0].split("+")[0].split("x")]

# read the screenshot

im = Image.open(path)

width, height = im.size

# get the mouse position

mousepos = int(get(["xdotool", "getmouselocation"]).split()[0].split(":")[1])

top = 0

bottom = height



if mousepos <= screenborder[0]:

    left = 0

    right = screenborder[0]

else:

    left = screenborder[0]

    right = width

# create the image

im.crop((left, top, right, bottom)).save(os.path.join(savepath, "cropped_"+name))

How to use

1. The script needs xdotool, to get the mouse position:

   
   
   

   sudo apt-get install xdotool
   
   

   
   
   

   Furthermore, not sure if python3-pil is installed by default:

   
   
   

   sudo apt-get install python3-pil
   
   



2. Copy the script above into an empty file, save it as crop_screenshot.py



3. In the head section of the script, set the desired name of the screenshot and the directory you use for your screenshots:

   
   
   

   # ---set the name of your (automatically numbered) screenshots (no extension)
   
   imagename = "screenshot"
   
   # ---set the path to where you (want to) save your screenshots
   
   savepath = "/home/jacob/Bureaublad"
   
   




4. Test- run the script from a terminal:

   
   
   

   python3 /path/to/crop_screenshot.py
   
   

   
   
   

   The result:

   
   
   

   




5. If all works fine, add it to a shortcut. Choose: System Settings > "Keyboard" > "Shortcuts" > "Custom Shortcuts". Click the "+" and add the command:

   
   
   

   python3 /path/to/crop_screenshot.py
   
   

Note

The script, as it is, simply splits the image on the width of your left screen. This is sufficient, because your screens are of the same y-resolution and aligned.

The script can however very well be edited to work with any screen arrangement, with any number of screens, as long as the screens are arranged in a non-overlapping arrangement. The math is a bit more complicated in that case however.

If anyone is interested, I will add it later.