Information about Screenshot

A screenshot, screen capture, or screen dump is an image taken by the computer to record the visible items displayed 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 bitmap image 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 (screencaps)

Capturing the screen over an extended period of time to form a video file. (see video capture)

History

Screenshots have been used since the 1970s to help market video games. Many game players have come to expect to turn over the game box in order to find out what the game looks like when you are playing it. They were never as widely used for computer applications, instead people relied on lists of features to determine if the program was interesting. Throughout the history of screenshots, there have been some deceptive practices, such as using a screenshot from a computer platform with better graphics on the box of a port to a lesser platform. Some games for the Commodore 64 would have screenshots from the Commodore Amiga version of the game and so on. Due to complaints by consumers, software companies began putting captions below games such as "Screenshot from Amiga version" or "Actual C64 screenshot".

In the 1990s, when pre-rendered or filmed videos became a part of intermissions in games, some game boxes included screenshots from the in game videos, which deceived consumers as to what the actual in game play looked like. Like before, consumer complaints brought about changes to the way screenshots appeared on boxes and in reviews. Screenshots began to have captions like "Actual in-game play".

Today, screenshots are expected for application software as well as games, especially when downloading software online that is graphical. More than before, decisions to use a piece of software are based on screenshots.

Internet uses

It has become popular in the internet fandom culture to use screencaps of movies and television shows in the creation of fanart, most commonly as icons for LiveJournal, MSN Messenger, and Internet forums about those topics. Websites and various communities have been created to distribute these screencaps.

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. These shortcuts also work in Mac OS Classic.

You can also use the Grab application to take screenshots.

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. The manual page (available via the command "man screencapture") explains all the options. This utility might only be available when the Mac OS X developer tools are installed.

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. Some programs, however, particularly multiplayer online games, will automatically save screenshots in a specified folder. As of Windows XP, it is no longer possible to take screenshots of full-screen DOS windows without other software.

The print screen button uses “keybd_event” API to capture screen.

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

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.

recordMyDesktop is a desktop session recorder for Linux that runs as a command line tool or with a GTK or Qt frontend (gtk-recordMyDesktop and qt-recordMyDesktop, respectively).

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 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, then clicking, "Advanced", "Troubleshoot", and moving the Hardware Acceleration Slider to "None."

DVDs are often encrypted using a patented algorithm called Content-scrambling system or CSS, making it much more difficult to take screenshots of them. Many DVD-capable media players will only play them on the overlay layer, where they cannot 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, as it is a derivative work of the widgets and other art created for the software.^[1][2]

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.

Screenshots may still be used under 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".^[3][4] Similar laws exist in other countries, such as fair dealing.

See also

• Screencast, Video capture
• Screenshot map
• Thumbshot

References

External links

• Screen Capture at the Open Directory Project
• Mac OS X Screenshot Secrets - O'Reilly
• How to Take Screenshots in Linux
• 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 for Windows
• 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