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A screen dump, screen capture (or screen-cap), screenshot (or screen shot), screengrab (or screen grab)  is an image taken by the computer user to record the visible items displayed on the monitor, television, or another visual output device. Usually, this is a digital image using the (host) operating system or software running on the computer, but it can also be a capture made by a camera or a device intercepting the video output of the display (such as a DVR). That latent image converted and saved to an image file such as to JPEG or PNG format is also called a screenshot.
Screenshots can be used to demonstrate a program, a particular problem a user might be having, or generally when display output needs to be shown to others or archived. For example, after being emailed a screenshot, a Web page author might be surprised to see how his page looks on a different Web browser and can take corrective action. Likewise with differing email software programs, (particularly such as in a cell phone, tablet, etc.,) a sender might have no idea how his email looks to others until he sees a screenshot from another computer and can (hopefully) tweak his settings appropriately.
On Mac OS X, a user can take a screenshot of an entire screen by pressing ⌘ Cmd+⇧ Shift+3, or of a chosen area of the screen by ⌘ Cmd+⇧ Shift+4. This screenshot is saved to the user's desktop, with one PNG file per attached monitor. If the user holds down ^ Ctrl while doing either then the screenshot will be copied to the clipboard instead.
Beginning with Mac OS X Tiger, it is possible to make a screenshot of an active application window. By following ⌘ Cmd+⇧ Shift+4, with pressing the Spacebar, the cross-hair cursor turns into a small camera icon. The current window under the cursor is highlighted, and a click on the mouse or trackpad will capture a screenshot of the entire highlighted element (including the parts offscreen or covered by other windows).
A provided application called Grab will capture a chosen area, a whole window, the whole screen, or the whole screen after 10 seconds and pops the screenshot up in a window ready for copying to the clipboard or saving as a TIFF. The Preview application, also provided, has the same capture options as Grab but opens the captured image immediately in a new window.
A shell utility called "screencapture" (located in
/usr/sbin/screencapture) can be used from the Terminal application or in shell scripts to capture screenshots and save them to files. Various options are available to choose the file format of the screenshot, how the screenshot is captured, if sounds are played, etc. This utility might only be available when the Mac OS X developer tools are installed. A user cannot capture the screen while DVD Player is running.
On Microsoft Windows, pressing Prt Sc captures a screenshot of the entire desktop and places it in the clipboard, while ⎇ Alt+⎙ PrtScr captures only the active window or active dialog box. In most versions of Windows, captured screenshots do not include the mouse pointer.
Once captured, the screenshot must be pasted from the clipboard into a separate program, such as Paint or GIMP, to be viewed or saved. Some programs, however—particularly multiplayer online games—will automatically save screenshots in a specified folder. As of Windows XP (or any version based on Windows NT), it is no longer possible to take screenshots of pseudo-"full-screen" DOS windows without other software. Windows 8 PCs are able to capture screenshots by pressing ⌘ Win+⎙ PrtScr, where the screen will briefly dim and automatically save a PNG file under the "Screenshots" folder in the user's "My Pictures" folder.
Video content in programs using a hardware overlay video renderer is not captured by the method described above. Older Windows Media Player on Windows XP in its default configuration on supported hardware is affected by this. But in Windows Media Player 9 and 10 a screen shot feature is built in and can be used by just pressing CTRL-i. The other method which is more useful if you want shots of the whole screen is to turn off the video acceleration. Also, some third-party applications can capture overlay images.
Windows Vista, Windows 7 and Windows 8 include a utility called Snipping Tool, first introduced in Windows XP Tablet PC Edition. It is a screen-capture tool that allows taking screenshots ("snips") of a window, rectangular area, or free-form area. Snips can then be annotated, saved as an image file or as an HTML page, or emailed. However, it does not work with non-tablet XP versions but represents an XP compatible equivalent.
Windows 7 also provides a "problem steps recorder" (psr) which records a screenshot every time the mouse is clicked. When stopped it creates a zipped MHTML document with all the screenshots inside.
In Windows Phone 8, screenshots can be taken by simultaneously pressing and holding the phone's sleep/wake button and Windows Start button. The screenshots are saved in the phone's native screen resolution under "screenshots" in the Photos hub. The screenshot functionality is only available for Windows Phone 8 or later.
A screenshot can be taken on iOS by simultaneously pressing the Home button and the Lock button; the screen will flash and the picture will be stored in PNG format in the "Camera Roll" on the iPhone or in "Saved Photos" on the iPod touch or iPad. The screenshot feature is available with iOS 2.0 and later.
Screenshots can be taken by pressing Volume Down+Power, and are saved in the "Screenshot" folder in the gallery after a short sound and visual effect.
On certain devices that use modified Android, the button combination and the storage location can be different. Some vendors have also implemented the screenshot functionality on earlier Android versions.
There is no direct way to take screenshots programmatically in non-system apps, however, on most devices, apps may use the system screenshot functionality without special permissions.
Screenshots of the HP webOS can be taken. For webOS phones, simultaneously press Orange/Gray Key+Sym+P. For the HP Touchpad, press ⇱+Power. In either case, screenshots will be saved to the "Screen captures" folder in the "Photos" app.
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 depending on the platform. While xwd(1) is the closest "standard" way of taking screenshots on the X Window System, other bundled utilities are easier to use. Some programs for creating screenshots on X Window System are:
On Maemo 5 a screenshot can be taken by pressing ^ Ctrl+⇧ Shift+P simultaneously. Screenshots will be saved as "Screenshot-YYYYMMDD-HHMMSS.png" in "Images/Screenshots" on the internal storage.
On Chromebook and related devices with the Chrome OS keyboard layout, pressing the equivalent of ^ Ctrl+F5 on a standard keyboard will capture the entire screen, and the equivalent of ^ Ctrl+⇧ Shift+F5 will turn the mouse into a rectangle select tool for capturing a custom portion of the screen.
On Windows systems, 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 by using a method called hardware overlay. Generally, there is no way to extract a computed image back out of the graphics card, though software may exist for special cases or specific video cards.
One way these images can be captured 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. In Windows XP, this is disabled by opening the Display Properties menu, clicking on the "Settings" tab, clicking, "Advanced", "Troubleshoot", and moving the Hardware Acceleration Slider to "None."
Free software media players may also use the overlay but often have a setting to avoid it or have dedicated screenshot functions.
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 frame/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, as it is a derivative work of the widgets and other art created for the software. Regardless of copyright, screenshots may still be legally used under the principle of fair use in the U.S. or fair dealing and similar laws in other countries.
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