One of the possibilities of taking screenshots in Linux is using

, a utility of the X Window System.

I just want to give a short overview on how to take interactive and non-interactive screenshots, view them and convert them to different formats.

Taking Screenshots

To take a screenshot you could just open a terminal and type ”

“, but by default

does not save the screenshot to a file (it outputs the image to stdout). To save the screenshot in a file, you can either use the

option of

:

xwd -out <filename>

or redirect the output of

to a file using the functionality offered by the shell:

xwd > <filename>

Just replace

with the name of the file you want to use for your screenshot. Examples:

xwd -out myshot.xwd

or

xwd > myshot.xwd

Notice the changed mouse pointer after typing one of these commands ? That’s because you now need to select the window of which you want to take a screenshot. The format

uses for the images it is called “X Window Dump” and the extension often used is

. I will cover the subject of converting the images to different formats (like JPEG or PNG) later.

Including the Window Frame

If you want to include the frame of the window in the screenshot, you have to add the

option. For example:

xwd -frame -out myshot.xwd

or

xwd -frame > myshot.xwd

Taking Screenshots Of The Whole Desktop

If you want to create a screenshot of the whole desktop instead of a single window, you can use the

option for that:

xwd -root -out myshot.xwd

or

xwd -root > myshot.xwd

Automated Screenshots Without Selecting The Window

It’s also possible to create screenshots of windows without the need to select them every time. This is especially useful if you want to make numerous screenshots of a single window (e.g. for a tutorial, a presentation, an article etc.).

To do this, you have to tell xwd which window you want to take a screenshot of on the command line, so that it does not have to ask. You can do this either by using the “resource id” of the window or the ”

property”. The value of the

property basically is the title of your window as it is displayed in the window title bar. Using this to create screenshots can be problematic (With Firefox, for example, this value depends on the title of the active tab, so going to a different tab will change the

property of the window).

To determine the resource id or the value of the

property, you can use the

tool. Just type this in the terminal:

xwininfo

And then, similar to

, click on the window you are interested in. It will then display a bunch of information about the window, which might look like this:

xwininfo: Window id: 0x40000e7 "Home of the Mozilla Project - Mozilla Firefox"

  Absolute upper-left X:  1287
  Absolute upper-left Y:  70
  Relative upper-left X:  0
  Relative upper-left Y:  0
  Width: 1159
  Height: 1501
  Depth: 24
  Visual: 0x21
  Visual Class: TrueColor
  Border width: 0
  Class: InputOutput
  Colormap: 0x20 (installed)
  Bit Gravity State: NorthWestGravity
  Window Gravity State: NorthWestGravity
  Backing Store State: NotUseful
  Save Under State: no
  Map State: IsViewable
  Override Redirect State: no
  Corners:  +1287+70  -114+70  -114-29  +1287-29
  -geometry 1159x1501+1279-21

The red and blue color was something I added for clarification. The red thing is the resource ID we are interested in and the blue thing is the

property that we also could use.

If we wanted to use the resource ID, we would do it like this

xwd -id  -out myshot.xwd

If we want to use the WM_NAME property, we would do this:

xwd -name  -out myshot.xwd

One important thing to note about this approach is that using the -frame option for xwd does not have any effect if you supply the id or name as well. That is, because the resource id for both cases is different. Therefore, if you want to include the window frame, you have to supply the

option to

to retrieve the correct resource id. You would then type:

xwininfo -frame

Just to show you that they really differ: In my case, right now, running

xwininfo

gives me:

xwininfo: Window id: 0x40000e7 "Home of the Mozilla Project - Mozilla Firefox"

while running

xwininfo -frame

and clicking on the same, unchanged window, gives me:

xwininfo: Window id: 0xe002df (has no name).

Viewing Screenshots

You can view the

-screenshots directly with the tool

. Just type:

xwud <filename>

for example:

xwud screenshot.xwd

Converting and Editing Screenshots

Converting Screenshots

You can easily convert the screenshots to “normal” image formats like JPEG or PNG with tools like ImageMagick. If you don’t have ImageMagick installed, it should be available through your repositories. For example, in Ubuntu/Debian you would simply type:

sudo aptitude install imagemagick

or

sudo apt-get install imagemagick

Once you have ImageMagick installed, you can convert an

image by using

. For example, to convert an

-screenshot named

to a JPEG file named

, type:

convert shot.xwd shot.jpg

You can convert the image to other formats as well, like PNG for example:

convert sot.xwd shot.png

Editing Screenshots

I won’t include a tutorial on editing screenshots here, but I just wanted to mention that you might not have to convert your screenshots to JPG or PNG (or something else) in order to edit them, because your image editor might already be able to load

files. GIMP, for example, can open them directly.