In computer graphics

Computer graphics

Computer graphics are graphics created using computers and, more generally, the representation and manipulation of image data by a computer with help from specialized software and hardware....

, a drop shadow is a visual effect consisting of drawing that looks like the shadow of an object, giving the impression that the object is raised above the objects behind it. The drop shadow is often used for elements of a graphical user interface

Graphical user interface

In computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...

 such as window

Window (computing)

In computing, a window is a visual area containing some kind of user interface. It usually has a rectangular shape that can overlap with the area of other windows...

s or menu

Menu (computing)

In computing and telecommunications, a menu is a list of commands presented to an operator by a computer or communications system. A menu is used in contrast to a command-line interface, where instructions to the computer are given in the form of commands .Choices given from a menu may be selected...

s, and for simple text. The text label for icons on desktops in many desktop environment

Desktop environment

In graphical computing, a desktop environment commonly refers to a style of graphical user interface derived from the desktop metaphor that is seen on most modern personal computers. These GUIs help the user in easily accessing, configuring, and modifying many important and frequently accessed...

s has a drop shadow, as this effect effectively distinguishes the text from any colored background it may be in front of.

A simple way of drawing a drop shadow of a rectangular object is to draw a gray or black area underneath and offset from the object. In general, a drop shadow is a copy in black or gray of the object, drawn in a slightly different position. Realism may be increased by:

1. Darkening the colors of the pixels where the shadow casts instead of making them gray. This can be done with alpha blending the shadow with the area it is cast on.
2. Softening the edges of the shadow. This can be done by adding Gaussian blur
   Gaussian blur
   A Gaussian blur is the result of blurring an image by a Gaussian function. It is a widely used effect in graphics software, typically to reduce image noise and reduce detail...
   
    to the shadow's alpha channel before blending.

External links

• Drop shadow definition at About.com
  About.com
  About.com is an online source for original information and advice. It is written in English, and is aimed primarily at North Americans. It is owned by The New York Times Company....
  
  
• A Drop-Shadow Primer at Webreference.com
  WebReference.com
  WebReference.com is a web site devoted to World Wide Web development. Created in 1995 by Athenia Associates, it is owned by Jupitermedia Corp as of 2005.-External links:* *...