Screenshot
A screenshot, screen dump, or screen capture is an image taken by the computer to record the visible items on the monitor or another visual output device, usually this is a digital image taken by the host operating system or software running on the computer device but it can also mean when a capture is made by an external device such as a Camera or something intercepting the video output of the computer.
A screenshot of the Wikipedia website taken of Mozilla 1.4 running Debian GNU/Linux and the XFree86 window system A thumbnailed screenshot of the Wikipedia website, taken on Debian GNU/Linux running the X Window system
Screenshots, screen dumps or screen captures can be used to demonstrate a program, a particular problem a user might be having or generally when computer output needs to be shown to others or archived, the most common of the three is a screenshot which commonly means outputting the entire screen in a common format such as PNG or JPEG.
Applications:
- demonstrating a program
- making an image file of an image shown by a program, in the case that that program does not have this feature itself; the screenshot can then be cropped to the image itself; a limitation is that for large images that do not fit on the screen one can not store the whole image; however, one can store it in pieces and then paste these together with a graphics editing program. This is rather cumbersome. To reduce this problem one can temporarily set a higher screen resolution.
Sometimes a screenshot does not work on a movie still presented by a movie viewer.
If the system seems frozen one may be looking at a full-screen screenshot image.
A screen dump is when the display system dumps what it is using internally upon request, such as XWD X Window Dump image data in the case of X11 or PDF in the case of Mac OS X. Finally a screen capture commonly means to capture the screen over an extended period of time to form a Video file.
Taking screenshots
There are numerous ways to take a screenshot on many operating systems, and applications this article attemts to cover the ones that use standard software on each platform to achive the task.
Microsoft Windows
In Microsoft Windows a screenshot of the entire monitor, complete with taskbar, can be copied to the system clipboard by pressing the Print Screen button. Alternatively, pressing ALT + Print Screen will copy just the active window to the clipboard.
Mac OS X
To save an image of the entire screen in Mac OS X pressing Command + Shift + 3 saves a PDF file on the desktop ( ~/Desktop/ ) containing a PDF Dump of the screen.
To take a picture of part of the screen pressing Command + Shift + 4 and then select the area to be captured.
To take a picture of a window or menu, press the space bar after Command + Shift + 4. By default, the captures are stored in PDF on the desktop. To copy the captures to the clipboard, press the control key along with the other keys.
X Windows
Since X Windows itself is not a desktop enviroment and only includes a very basic set of programs it is not common for the basic xwd(1) to be used, most people use other bundles utilities to achive the task.
xwd
On systems running X Windows the standard utility to dump an image of an X Window is xwd(1), xwd produces XWD X Window Dump image data. It can be invoked in the following way:
xwd -root -out root.xwd
xwd can also be used to dump a single window if provided with the -id option followed by the corresponding window id, for further info see man 1 xwd [1]
ImageMagick
Alternatively if you have ImageMagick installed the following command can be used to import the root window and everything above to a PNG image file called root_window.png, it uses the convert(1) utility.
import -window root root_window.png
KDE and GNOME
In the K Desktop Enviroment, the built-in program KSnapshot is the default screen grabbing utility. GNOME users can also use the Screen-Shooter applet or press 'print screen'.
GIMP
The GIMP can also be used to take screenshots on any platform it is available on, simply navigate File->Acquire->Screenshot on the toolbox menu to capture either the current screen or choose timed mode.