Getting to Know Flash Pro

Graphics used on the Flash Stage can be classified into two main categories: non-symbols and symbols. This section examines each category.

Bitmapped graphics can be imported from sources ranging from digital photos to user-created graphics developed on drawing applications. Bitmapped graphics are weightier than vector graphics in most cases, and Flash has an option for transforming bitmapped graphics into vector graphics (by selecting Modify, Bitmap, Trace Bitmap). Vector graphics are preferred both because of their lighter weight and because of their ability to be changed dynamically without distortion. All graphics created with Flash tools are vector graphics. We'll get into more detail on this topic in later chapters.

Symbols are a key element in Flash's ability to send graphics and animations over the Internet using minimal bandwidth. When a drawing is converted into a symbol, only a single symbol is compiled into the SWF files. Multiple instances of a single symbol can be used in a Flash document, but the bandwidth costs associated with the symbol are only "charged" once, no matter how many instances of the symbol are used in the Flash file. Figure 1.12 illustrates the difference between how symbols and drawings add to a SWF's file size.

Figure 1.12 Multiple instances of a single symbol require less bandwidth.

Movie clips are movies within a Flash movie. They have their own Timelines and act as independent entities within a Flash movie. They can communicate with other movie clips and with other elements of a Flash movie. In Flash Pro, they're symbols that can be created on the Stage using drawing tools and converted using the Convert to Symbol dialog box, and they're also classes. (Alternatively, you can create them by selecting Insert, New Symbol and choosing Movie Clip. They are placed into the Library panel, where you can drag them to the Stage.) As a class, movie clips can be created dynamically during runtime, and you can link a movie clip on the Stage with a class using the movie clip's Symbol Properties dialog box. For example, Figure 1.13 shows two movie clips on the Stage of a main movie.

Figure 1.13  Movie clips have their own Timelines.

On the main Timeline, the two movie clips are rotated (rectangle) or moved up and down (circle). Within the rectangle movie clip, on the movie clip's Timeline, a ball moves from corner to corner. The circle movie clip has a rectangle that moves from side to side. Chapter 5 provides more details about this important Flash feature.