Learning Flash CS4 Professional

Chapter 7. FILTERS AND BLEND MODES

Introduction

Although many designers and developers like to capitalize heavily on Flash’s vector-based features, the application has a lot to offer from the world of pixels. Perhaps the most useful way in which vectors and pixels coexist in Flash is through the use of bitmap compositing features. In this context, compositing pertains to combining visual elements to give those elements a new appearance. This includes the use of transparency, blending (combining the pixel color values of two bitmaps), and filters (such as blur or drop shadow). Whether your asset is a bitmap or vector, Flash can use traditional bitmap compositing techniques to combine elements during authoring or at runtime.

Bitmap Caching

Flash can act upon vectors as if they were bitmaps by using a feature called bitmap caching. Bitmap caching is a process by which Flash Player temporarily takes a bitmap snapshot of your asset and uses that snapshot, rather than the original asset, for bitmap compositing. There are two important ideas going on here. First is the concept that you can apply an effect typically reserved for bitmaps, such as blurring, to vectors. Second is the fact that the effect is applied to a cached snapshot of the original asset, which means the asset remains in its original format. For example, if the original asset is a vector, it remains crisp at any resolution.

Bitmap caching not only makes certain features possible, it can also improve performance. This is because ...