Since its introduction in 1996, Flash has grown in popularity to become widely regarded as a standard for high-end multimedia Web sites and presentations. Flash was derived from other Macromedia applications, particularly FutureSplash and Director. Macromedia Director has a longer history, but is primarily used for multimedia development for CD-ROMs, movies and television. However, the files created by Director are too large to port effectively over the Web.

Flash offers many of the dynamic features that Director offers, yet Flash compresses file sizes, making it possible to offer media-rich content and fast download times.

How does Flash work?

Flash combines four elements that define its functionality: vector graphics, streaming capability, a timeline, and layers.

Concepts and issues relevant to Flash

Vector graphics

Flash uses vector graphics, rather than bitmapped graphics such as GIF, JPG or PNG. Vector graphics perform more efficiently on the Web because they are based on mathematical computations, rather than the pixel-by-pixel information used by bitmaps.

As such, Flash graphics are scalable without affecting file size. For example, suppose that the two circles in Figure 23-l are separate vector graphics being displayed in a browser. Both images would have the same file size. The only difference between the two circles is the radius, which can be adjusted by a mathematical calculation. Vector graphics use mathematics in this way to manipulate images.



By contrast, if these images were bitmaps, the larger circle would have a significantly larger file size than the smaller one.

Streaming capability

In addition to using vector graphics, Flash offers another important feature that increases its Web compatibility: streaming capability. Streaming allows multimedia content to begin playing as soon as it reaches its destination-in this case, the client browser. For example, suppose a Flash file (also known as a Flash movie) has a total size of 100 KB. Using a standard 28.8-Kbps modem, a user must wait approximately 28 seconds for the entire file to download before the movie can begin to play. With streaming capability, the movie begins as soon as the initial information about the Flash file reaches the browser. This means that the user can begin watching the movie while the rest of the data continues to download.

Timeline

Flash uses the combination of vector graphics and streaming capability to deliver animation that is created using a timeline. The Flash Timeline can be thought of as a series of movie frames. As you develop more frames (or longer timelines), the movie begins to take action. Each Flash movie is a timeline consisting of a series of frames. Each frame contains vector graphics that are opened at a designated sequence and speed, creating the animation.

Layers

The final component of a Flash movie is layers. Each movie can have multiple layers, thus providing animation that is not only linear but also parallel: One animation sequence runs on top of another because each is on a different layer.

Flash and the browsers

Currently, Flash is not natively supported in browsers. Therefore, for a user to play Flash movies, his or her browser needs a plug-in. Because Flash does not rely on the browser, it is cross-platform capable, which is another advantage.

NOTE: IMPORTANTLY, MACROMEDIA IS WIDELY THOUGHT TO HAVE BEEN BANKING ON NATIVE SUPPORT IN BROWSERS, PARTICULARLY MICROSOFT. THIS HAS NOT HAPPENED AND IT FORMS THE BASIS OF THE QUESTION OF WHETHER FLASH WILL GAIN IN POPULARITY OR NOT. DISCUSS IN YOUR TUTORIAL WHETHER USERS ARE BECOMING ANY MORE INCLINED TO WANT TO DOWNLOAD PLAYERS TO READ WEB PAGES.

According to a study at the beginning of 2000, Flash had an installation base of 68 percent, or approximately 195 million users who have the Flash plug-in. There are two reasons for this. One is that many sites use Flash, and therefore many users have downloaded the plug-in. The second reason is that the 4.x versions of both Navigator and Internet Explorer include the Flash plug-in installed by default. AOL and WebTV also provide some Flash support in their browsers.

How Flash works with HTML

When you create a Flash movie, you have a file with the .fla file name extension (on the Windows platform). The FLA file format can then be converted and compressed into a SWF (pronounced "swiff"), which is then inserted into the HTML code using the <OBJECT> tag (for Internet Explorer) or the <EMBED> tag (for Navigator) to display in the browser. When the browser encounters the SWF file, the Flash plug-in is used to display the Flash movie in the browser.

Thus, the only HTML code on which Flash relies is the <OBJECT> and <EMBED> tags.

Some sites are created entirely with Flash, while others use Flash to provide simple animation such as navigation menus and rollover effects. Therefore, while Flash does not rely on HTML, the two technologies can co-exist and complement each other.