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Screenshot

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A screenshot

A screenshot, screen capture, or screen dump 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 be a capture made by a camera or a device intercepting the video output of the computer.

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.

All three terms are often used interchangeably; however, some people distinguish between them as follows:

Screenshot
Outputting the entire screen in a common format such as BMP, PNG, or JPEG.
Screen dump
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. As of Mac OS X 10.4, pictures are no longer saved as PDF. They are saved as PNGs.
Screen capture
Capturing the screen over an extended period of time to form a Video file. (see video capture)

Uses of screen captures

It has become popular in the internet fandom culture to use screen captures (usually referred to as "screencaps") of movies and television shows in the creation of fanart, most commonly as icons for LiveJournal or MSN Messenger. Websites and LiveJournal communities have been created to distribute these screencaps. Static screen capture represents a snapshot of a PC screen at a given time stored into a file, operating system clipboard, or embedded into a document.

Screencaps can be easily done using programs like Media Player Classic (which allow you to save screenshots of video) or VirtualDub (which allows you to save a sequence of screenshots)

Built in screenshot functionality

Mac OS X

Pressing Command-Shift-3 takes a screenshot of the entire screen, and Command-Shift-4 takes a screenshot of a chosen area of the screen or if you press Space afterwards you can choose a window on the screen to individually screenshot. These images are saved to the desktop, but if you hold down the control key with the rest of the keyboard shortcut, the pictures are copied to the clipboard instead.

You can also use Grab to take screenshots.

The shortcuts also work in Mac OS Classic.

Microsoft Windows

Pressing the Print Screen key captures a screenshot of the entire desktop area, and places it in the clipboard. Pressing the combination of Alt-Print Screen captures only the current active window. Screenshots captured this way do not include the mouse pointer. By default, Windows does not save the screenshot to an image file; the user is required to paste the image into a separate imaging program (such as Microsoft Paint which is built-in) for saving. Unfortunately as of Windows XP, it is no longer possible to take screenshots of full-screen DOS windows without other software.

Windows Vista includes a utility called Snipping Tool, first introduced in Windows XP Tablet PC Edition. It is a screen-capture tool, that allows for taking screenshots (called snips) of windows, rectangular areas, or a free-form area. Snips can then be annotated, saved as an image file or as an HTML page, or emailed.

For programmatic access, application developers can use GDI, DirectX or the Windows Media Encoder API to capture the screen.

X Window System

gnome-screenshot (german version) in Ubuntu Linux 6.06 LTS using Gnome 2.14.3

Since X Window System itself is not a desktop environment and only includes a very basic set of programs, methods of taking screenshots vary greatly on the platform. While xwd(1) is the closest "standard" way to do it in the X Window System, most people use other bundled utilities to achieve the task due to their ease of use.

Video screen captures

None of the major operating systems have built-in mechanisms to record videos of the screen (recording how the user moves his mouse around, clicks icons, types text etc. as a movie). A multitude of utilities have come up to fill this void, though.

One program of note is Camtasia, which has a number of useful features.

Third party screenshot software

There are many third-party programs available on different platforms to take screenshots with advanced functionality. Some computer graphics software (e.g., IrfanView, GIMP, and PSP) can acquire screenshots. Typically, these programs can be configured to include or exclude the mouse pointer, automatically crop out everything but the client area of the active window, take timed shots, areas of the screen not visible on the monitor (autoscroll), and so on.

Common technical issues

Hardware overlays

Screenshots of games and media players sometimes fail, resulting in a blank rectangle. The reason for this is that the graphics are bypassing the normal screen and going to a high-speed graphics processor on the graphics card called the hardware overlay. Generally, there's no way to extract a computed image back out of the graphics card, though software may exist for special cases or specific video cards.

The trick to capturing those images is to turn off the hardware overlay. Because many computers have no hardware overlay, most programs are built to work without it, just a little slower. Here's a quick way to switch off the hardware overlay in Windows XP. Open Display Properties, Click Advanced, Click the Troubleshoot Tab, and Move the Hardware Acceleration Slider to "None." The hardware overlay is now disabled.

Store-bought DVDs are a special case because they're encrypted using a patented algorithm called Content-scrambling system (CSS). Many DVD-capable media players (including Windows Media Player), but not all (PowerDVD, WinDVD, and Media Center to name a few), will only play DVDs on the overlay layer, where they can't be captured.

Screen recording

The screen recording capability of some screen capture programs is a time-saving way to create instructions and presentations, but the resulting files are often large.

A common problem with video recordings is the action jumps, instead of flowing smoothly, due to low frame rate. Though getting faster all the time, ordinary PCs are not yet fast enough to play videos and simultaneously capture them at professional frame rates, i.e. 30 frame/s. For many cases, high frame rates are not required. This is not generally an issue if simply capturing desktop video, which requires far less processing power than video playback, and it is very possible to capture at 30 frames/s. This of course varies depending on desktop resolution, processing requirements needed for the application that is being captured, and many other factors.

Some companies believe the use of screenshots is an infringement of copyright on their program. This is one of the issues "solved" by Trusted Computing. Under Trusted Computing, programs will be able to block the taking of screenshots of their windows. Countering this argument is the principle of fair use, which (in U.S. law) permits copying of images or text for 'criticism, comment, news reporting, teaching, scholarship, or research.'

See also

  • Screen Capture at Curlie
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