Chapter 6. Composing Images with Bitmaps and Masks

Flash is primarily a vector editing program. Yet it can import other types of media, such as bitmap graphics, sound, and video, and it has limited tools for working with these media. To work well with import media such as bitmaps and sounds, you need to understand not only the intrinsic strengths and limitations of each form of media, but also the ways that Flash works with them.

In most cases, vector graphics are preferable to bitmap graphics for use in Flash. Vector graphics are smaller in file size as well as easier to edit and modify than bitmap graphics. In addition, bitmap graphics do not scale well, usually making them look unacceptable in Flash movies that resize to fit the size of the browser window. But sometimes bitmaps are unavoidable, especially when you need to use digital photography.

Although it is possible to convert bitmap graphics to vector graphics, using a process called tracing, and discussed in this chapter in Recipe 6.4, the converted graphic is often worse than the original in file size, editability, and visual quality.

Bitmap graphics may not be the Flash developer's first choice, but they are a common feature of Flash movies. Because of Flash's limited bitmap editing abilities, you should try to finalize them in a bitmap editing program, such as Macromedia Fireworks, Adobe Photoshop, or Jasc Paint Shop Pro. That is, you should set the resolution, image dimensions, tonal balance, and so on before you import the image into Flash. You can erase or paint over bitmap pixels in Flash, but that is about the limit of Flash's authoring time bitmap editing abilities.

Bitmap graphics, along with sounds and video, can increase a Flash movie's file size quite rapidly. Optimization is an important task when working with bitmap graphics. By default, Flash compresses bitmap graphics upon export. You have control over this compression and can also disable it, on a one-by-one basis, in the event that you have optimized your graphics in an external program, such as Fireworks or ImageReady.

But Flash has some advantages of its own. For one, it can animate image compositions. For example, you can create a mask, and then animate that mask or the masked content. In addition, you can script the behavior of masks, enabling dynamic masks that respond to user-initiated events during playback.