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The Basics of Digital Images

An image, of course, is any visual representation. Still
images, such as photographs and drawings, capture a
single, visual moment in time; while moving and video
images, such as television and movies, are able to capture
entire periods of time.

A digital image is simply an image that can be represented
in a computer's numeric, or digital, language. A digital image
is composed of millions of tiny dots called pixels. If you look
closely at a computer monitor, you can probably see these
tiny dots at the edges of curved images, such as letters, for
example. These pixels can be displayed as any one of
several million colors, and when all of the pixels are placed
in the right order, they form an image.

The proper ordering and coloring of these pixels is often stored
in a file on a computer. Image file types--such as GIF, JPG,
BMP, EPS and others--simply use a slightly different technique
for describing the proper order and color of the pixels that
comprise a given image. Videos--which are a series of still
images--are stored in formats that can support information for
a soundtrack that goes with the video.

Image files are saved using different formats. For still images
alone there are nearly 100 different file formats. Each format
offers its own compression technique and image quality for a
variety of practical applications. Here are the most common
file formats for still images and a brief description of their
common use.

# JPEG (Joint Photographic Experts Group)
# GIF (Graphics Interchange Format)
# TIFF (Tapped Image File Format)
# BMP (Bitmap File)
# EPS (Encapsulated PostScript)
# Al (Adobe Illustrator)
# SVG (Scalable Vector Graphics)

To enable the sharing of such a photo, one solution is to
compress the photographic data (data that represents the
photo), meaning rearranging the data and reducing the number
of colors in the photo so that the data takes up less space.
This technique is used by the Graphics Interchange Format
(GIF) file format.

Although the GIF image appears less detailed than the original
raw photo--a result of the compression and reduction in color--
the GIF image takes up only 68,000 bytes of storage. This size
is a reasonable size for sharing the photo. To enable file sharing
of a more detailed image, the developers of the JPEG format
came up with a more sophisticated way of compressing data.
They realized that the human eye cannot distinguish every
possible shade of color or every detail; thus, they developed a
technique that reduces a photo's colors and complexity without
the appearance of having done so. In other words, the only data
eliminated in the JPEG technique is data that your eye would not
process. The image below shows an example. As you can see,
this photo is much more lifelike than the GIF version, and it takes
up less storage space. Digital images play a very important role
in designing websites, choosing right format enables users to
view your website fast. Learn more about digital images and
creating websites.

Article written by David Manson.