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Screenshot

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A screenshot of this page being displayed in the Mozilla web browser.

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 be a capture made by an external device such as a camera or something 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.

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.

Taking screenshots

There are numerous ways to take screenshots on many operating systems and applications. This article attempts to cover the ones that use standard software on each platform to achieve the task.

Mac OS

In all versions of Mac OS up to and including Mac OS 9, the user simply hits shift-command-3: this puts a PICT file of the screen in the root folder of the boot volume, starting with a file called "Picture 1". Shift-command-4 allows the user to make a marquee selection of the screen. The screen capture is accompanied by a sound effect of a camera shutter as it takes a picture (Grab, detailed below, continues this tradition). Holding the control key causes the screenshot to be placed into the clipboard instead of being saved to disc.

If caps lock is enabled when shift-commmand-4 is pressed, the cursor becomes a form of bulls-eye and this allows a particular window to be captured simply by clicking on the window. Only the visible part of the window is captured, unlike Mac OS X where even the obscured and off-screen parts of the window are included in the screenshot (taken from the OS's buffer of the window contents, which was not present in Mac OS 9 and earlier).

Mac OS was rather atypical in that the mouse cursor was always included in screenshots of the complete screen. For screenshots of a region of the screen or a window, the cursor is needed to select the region or window to be captured and the cursor is not included in the picture as a result. Unlike Grab in Mac OS X, the current cursor is used: there is no need to select the cursor to be used in advance according to what cursor you believe will be in use at the time the screenshot is taken.

While the file format and location for the saved images changed with Mac OS X, the two primary keyboard shortcuts remain the same in Mac OS X. However, the activation method for window capture changed from caps lock pressed in advance, to space being pressed after shift-commmand-4 is itself pressed, and acts as a toggle between capturing a region and capturing a window.

Mac OS X

Mac OS X offers several means to take a screenshot :

Using Mac OS keyboard shorcuts:

  • shift-command-3 will capture the full screen, and place screenshot files on the desktop. If you work in a multi-screen configuration, one file will be created for each screen.
  • shift-command-4 will allow you to capture part of the screen: after pressing those three keys, your cursor will become a small crosshair, and you will be able to select the region of the screen to capture. If you press the space bar, the cursor will become a camera, with which you may select a window to be captured (including the windows used for menus, the menubar, desktop icons etc). The item to capture will be highlighted as you pass your mouse over it.

If you hold the control key (ctrl) while taking the screenshot, the resulting image will be placed into the clipboard instead of saved to a file. You can then paste it into another application.

In Mac OS X v10.4 "Tiger", the files created using this method are PNG files by default. It is possible to change this setting using the command line: in the Terminal, type:

defaults write com.apple.screencapture type image_format

where image_format could be BMP (Windows bitmap), GIF, JPEG 2000, JPEG, PDF, PICT, PNG, PSD, SGI, TGA & TIFF.

Using other applications:

  • The Grab application shipped with Mac OS X supports one more option – to take timed screen captures – and permits – via the Preferences – to place a cursor in the picture. Note that it does not include the actual cursor, but draws the user's chosen cursor at the cursor co-ordinates. Prior to Mac OS X, the mouse cursor was automatically included in full-screen captures but not captures of screen areas or individual windows where the cursor is used to select the area or window to capture. Grab places the screen capture into a new window, and you may save the image to disc as TIFF (but not any other format).
  • Preview version 3 (Mac OS X v10.4) now has an option to take window, selection and timed screen captures via File > Grab. Preview simply activates the OS's existing screenshot system, but saves the captures as TIFF files instead of PNG and opens them as soon as they are saved.

Both Grab & Preview automatically save the files as TIFF.

  • Many commercial programs can be used instead, which adds functionality such as capturing a video of the screen.

Screenshots cannot be taken while protected DVDs are playing in DVD Player. You can also perform screenshots of Exposé in operation, and take screenshots of the process of taking screenshots: press shift-command-4 and then space to enter window screenshot mode, hold the cursor over a window, and press shift-command-3 to capture the full screen. Because the camera cursor during window capture is not a real mouse cursor, it, too, is included in the screenshot. You will now wish to hit escape to cancel out of window capture mode.

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 key. Alternatively, pressing Alt + Print screen will copy just the active window to the clipboard. One can then paste the clipboard into a program such as MS Paint or Paint.NET to save it as an image file (for posting online, for instance), or paste it directly into a document. If saving as an image file, it is best to use a format which uses lossless compression (e.g. PNG) or no compression (e.g. BMP). Use a format which supports 24-bit color if the screenshot contains many colors.

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.

There are two ways to turn off the overlay. The usual way is to turn it off in the settings for the specific game or media player.

One can also turn off the hardware overlay globally through Windows. On Windows XP, go to Display Properties > Settings Tab > Advanced Button > Troubleshoot Tab. Set the Hardware Acceleration slider to one of the first three notches.

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.

Scroll capture

Often a page or list doesn't show on your screen all at once; you must scroll to see it all. To capture those areas intact, use the scroll capture tool offered by some vendors. This tool captures the entire page or list, automatically scrolling vertically and/or horizontally as required.

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. The professional way to create small, efficient demos is to build them from scratch in a Macromedia Flash editor, such as SwiSH Max., but this takes much more work.

Some sophisticated screen recording programs minimize file size by capturing only frames that change. In practice, you end up manually adding frames and doing other editing, so these programs fall mid-spectrum between simple recorders and building from scratch. One popular screen recording application that makes use of this is Camtasia Studio, by means of the proprietary TSCC codec.

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. For those who must have frame rates of 30 or above, one safe solution (though lower in overall quality) is to point a camcorder at the screen or to record on a VCR connected to the TV-Out on your graphics card.

X Window System

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.

xwd

On systems running the X Window System the standard utility to dump an image of an X Window is xwd(1), xwd produces an XWD image. It can be invoked in the following way:

xwd -root -out root.xwd

xwd can also be used to dump a single window selected with the mouse or provided with the -id option followed by the corresponding window id; for further info see man 1 xwd [1]. When run remotely, xwd is useful for taking screen shots of modal menus in action. The GIMP can be used to convert an XWD file to other more common formats such as PNG; equivalently, the command-line utility xwdtopnm, part of the Netpbm utility suite, can be used to convert the XWD file to PNM format, from which it can be converted to any common format, for example with the following pipeline:

xwd | xwdtopnm | pnmtopng > screendump.png

It is also possible to convert an XWD image into many other formats using the convert utility[2]: convert root.xwd root.XYZ, where XYZ is a typical filename-extension for a desired format.

KDE

In the K Desktop Environment, the built-in program KSnapshot is the default screen grabbing utility.

GNOME

GNOME users can take a screenshot either by selecting "Take Screenshot..." from the "Actions" menu (in GNOME versions older than 2.10), by selecting "Take Screenshot" from the "System..." menu (GNOME 2.10 or greater), by using the screenshot applet or by using one of the following two keyboard shortcuts, configured in Preferences → Keyboard Shortcuts:

  • Print Screen, to take a screenshot of the entire screen, or
  • Alt + Print Screen, to take a screenshot of the currently active window.

The screenshot is saved in PNG format.

ImageMagick

The import command from the widely used ImageMagick suite can be used for creating screenshots. A simple command to capture the screen is

import -window root screenshot.png

Screenshot software

There are many third-party programs available on different platforms to take screenshots with advanced functionality. Most computer graphics software (e.g., IrfanView, GIMP, and Photoshop) 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.

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. See also: Screencast.

Windows

Video screen capture tools include Fraps [3], SnagIt [4], Screen Shot Maker [5], 5 Clicks [6], Growler Guncam [7], Capture Professional [8], Bulent's Screen Recorder(BSR) [9].

Mac OS X

Third-party utilities to do video screen captures include Snapz Pro X (versiontracker info), Screentool (info) and ScreenBroadcasting (info).

Linux

Video screen capture tools include vnc2swf (GPL) [10] and Xvidcap [11].

Copyright issues

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.'

Screen capture software

MS Windows

Lists

Freeware and free software applications

Shareware and commercial applications

  • Screen recording (captures video and audio)
    • Bulent's Screen Recorder [13], includes screen video/audio capturing and video/audio editing for adding annotations, images, video, callouts, transitions, effects etc. into videos.
    • Camtasia Studio, by TechSmiths.
    • Growler Guncam [14]Can capture desktop programs or games, and includes editor. Can save as AVI or animated GIF.
    • HyperCam, by Hyperionics.
    • SnagIt [15], by TechSmiths. Includes both snapshots and video capturing to AVI, as well as editing. PC editors choice [16].
    • Screen Capture Video Easy Screen Capture Video is a professional quality video production studio designed to capture and record screen activity in real time.

Linux and Unix

Mac OS X

Others

  • Websnapr - on-line capturing of HTML pages
  • Girafa.com - Screenshot creator for blogs and websites.
  • [17] -An example Of a wikipedia screenshot

See also

External links

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