Ubuntu – Taking screenshot of a specific area from the command line

command linelubuntuscreenshot

I am running Lubuntu desktop 12 and I am looking for a tool that can take screenshots of a certain area from the command line.

I have tried out Shutter. It works but, when I run the command it generates warnings ( Wnck-WARNING **: Unhandled action type). I think the tool might be designed to run under GNOME and might not be compatible with Lubuntu. The screenshot is taken successfully, but the command hangs, which is something I cannot work with.

So what is a good screenshot tool that

  1. Runs from the command line
  2. Can capture a certain area of the desktop

I like to add that scrot, the tool Lubuntu ships with, does not have the option to crop certain coordinates, but only an interactively user-defined area which is not what I'm looking for.

Best Answer

In Lubuntu, you can do exactly what you want: take a screen shot from the command line with the command:

scrot_extended 100 100 400 400

using the script below.

The four arguments are <x>, <y>, <width>, <height>.
I didn't have the chance (yet) to test it in Lubuntu 12.04, but it seems unlikely it wouldn't work; it uses python 2 and basic command line tools that exist for a long time already.

Explanation

The script:

  • takes a screenshot with scrot
  • saves it into a temporary file
  • using imagemagick, it creates a new image, cropping the screen shot, with the arguments you ran the script with
  • the image is saved into a directory as a numbered file, to prevent overwriting

How to use

  1. The script uses both scrot and imagemagick. scrot should be on your system. To install imagemagick:

     sudo apt-get install imagemagick

  2. Copy the script into an empty file

  3. By default, images are saved to ~/scrot_images, named: outputfile_1.png, outputfile_2.png etc. . Change it if you want, as marked in the script. Note that if you change the diretory, you have to use the full path.

  4. Save the file to ~/bin (create the directory if needed) as scrot_extended (no extension) and make it executable.

  5. Log out and back in and take your screenshot with the command:

     scrot_extended <x> <y> <width> <height>

Example:

scrot_extended 100 100 400 400

enter image description here

outputfile:

enter image description here

The script

#!/usr/bin/env python
import subprocess
import os
import sys
# setting default directories / filenames
home = os.environ["HOME"]
temp = home+"/"+".scrot_images"
img_in = temp+"/in.png"
# if you prefer, you can change the two line below:
output_directory = home+"/"+"scrot_images" # output directory
filename = "outputfile"                    # filename
# creating needed directories
for dr in [temp, output_directory]:
    if not os.path.exists(dr):
        os.mkdir(dr)
# creating filename (-number) to prevent overwriting previous shots
n = 1
while True:
    img_out = output_directory+"/"+filename+"_"+str(n)+".png"
    if os.path.exists(img_out):
        n = n+1
    else:
        break
# reading arguments,arranging commands to perform
coords = sys.argv[1:5]
cmd1 = ["scrot", img_in]
cmd2 = ["convert", img_in, "-crop", coords[2]+"x"+coords[3]+"+"+coords[0]+"+"+coords[1], "+repage", img_out]
# Take screnshot, crop image
for cmd in [cmd1, cmd2]:
    subprocess.call(cmd)
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