Scaling and caching symbols

You can scale items on the stage in these ways:

• Scale individual symbol instances with the Free Transform tool, Properties panel, or Transform panel.

• Scale individual symbol instances with 9-slice scaling and the tools and panels listed above.

• Scaling the entire contents of the Stage when resizing the stage.

9-slice scaling allows you to specify how scaling is applied to specific areas of a movie clip. With 9-slice scaling, you can ensure that the movie clip looks correct when scaled. With normal scaling, Animate rofessional scales all parts of a movie clip equally, and in both the horizontal and vertical dimensions. For many movie clips, this equal scaling can make the clip’s graphics look strange, especially at the corners and edges of rectangular movie clips. This is often true of movie clips used as user interface elements, such as buttons.

The movie clip is visually divided into nine sections with a grid-like overlay, and each of the nine areas is scaled independently. To maintain the visual integrity of the movie clip, corners are not scaled, while the remaining areas of the image are scaled (as opposed to being stretched) larger or smaller, as needed.

When a movie clip symbol has 9-slice scaling applied, it appears in the Library panel preview with the guides displayed. If Enable Live Preview is turned on (Control > Enable Live Preview) when you scale instances of the movie clip on the Stage, you see the 9-slice scaling applied on the Stage.

note: The Live Preview setting cannot be used with an ActionScript 3.0 document.

A 9-slice-enabled movie clip can contain nested objects within it, but only certain types of objects inside the movie clip properly scale in the 9-slice manner. To make a movie clip with internal objects that also adhere to 9-slice scaling when the movie clip is scaled, those nested objects must be shapes, drawing objects, groups, or graphic symbols.

By default, slice guides are placed at 25% (or one-fourth) of the symbol’s width and height from the edge of the symbol. In symbol-editing mode, the slice guides appear as dotted lines superimposed on the symbol. The slice guides don’t snap when you drag them on the pasteboard. The guides do not appear when the symbol is on the Stage.

You cannot edit 9-slice-enabled symbols in place on the Stage. You must edit them in symbol-editing mode.

note: Instances made from a 9-slice-enabled movie clip symbol can be transformed, but should not be edited. Editing these instances can have unpredictable results.

Runtime bitmap caching lets you optimize playback performance by specifying that a static movie clip (for example, a background image) or button symbol be cached as a bitmap at runtime. By default, Flash Player redraws each vector item on the Stage in every frame. Caching a movie clip or button symbol as a bitmap prevents Flash Player from having to continually redraw the item, because the image is a bitmap and its position on the Stage does not change. This provides a significant improvement in playback performance.

For example, when you create an animation with a complex background, create a movie clip containing all the items included in the background. Then select Cache as Bitmap for the background movie clip in the Property inspector. During playback, the background is rendered as a bitmap stored at the current screen depth. Flash Player draws the bitmap on the Stage quickly and only once, letting the animation play faster and more smoothly.

Without bitmap caching, the animation might play back too slowly.

Bitmap caching lets you use a movie clip and freeze it in place automatically. If a region changes, vector data updates the bitmap cache. This process minimizes the number of redraws that Flash Player must perform, and provides smoother, faster playback performance.

Only use runtime bitmap caching on static, complex movie clips in which the position, but not the content, of the movie clip changes on each frame in an animation. The playback or runtime performance improvement from using runtime bitmap caching is only noticeable on complex-content movie clips. Runtime bitmap caching with simple movie clips does not enhance performance.

Guy Watson has written a detailed article about using bitmap caching in the Animate Developer Center titled Using Bitmap Caching in Animate.

Under the following circumstances, a movie clip does not use a bitmap (even if Use Runtime Bitmap Caching is selected) but instead renders the movie clip or button symbol by using vector data:

• The bitmap is too large (greater than 2880 pixels in either direction).

• Flash Player fails to allocate memory for the bitmap (producing an out-of-memory error).

When Bitmap Caching is turned on for a symbol instance, you can choose an opaque background color for the instance. By default the background is transparent.