From Wikipedia, the free encyclopedia
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:
- 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.
 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 are pasted as images on the desktop and if you hold down the control key as well they are copied to the clipboard instead.
You can also use Grab to take screenshots.
The shortcuts also work in Mac OS Classic
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. By default, Windows does not save the screenshot to an image file; the user is required to paste the image into a separate program for saving. Unfortunately as of XP it is no longer possible to take screenshots of full-screen DOS-windows without other software.
Vista includes a utility called Snipping Tool, first introduced in Windows XP Tablet PC Edition. It's a screen-capture tool, that allows for taking screen shots (known as 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.
 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.
- KSnapshot is the default screen grabbing utility in the K Desktop Environment.
- gnome-screenshot is the default screen grabbing utility in GNOME.
 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.
 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.'
 See also
 External links
- Screen Capture at the Open Directory Project (suggest site)
- Screen Capture Software at the Yahoo! Directory
- Mac OS X Screenshot Secrets - O'Reilly
- How to take screenshots from DVD using free tools
- How to make sequential thumbnails of a video using free tools
- In-depth review of Screen Capture Tools
- How To Capture a Screen Shot of your Desktop or the Active Window in Windows About.com step-by-step tutorial
- How To Capture a Screen Shot with the Snipping Tool in Windows Vista About.com step-by-step tutorial