cacheAsBitmap (MovieClip.cacheAsBitmap property) -- Flash CS3

If set to true, Flash Player caches an internal bitmap representation of the movie clip. This can increase performance for movie clips that contain complex vector content.

All vector data for a movie clip that has a cached bitmap is drawn to the bitmap instead of to the main Stage. The bitmap is then copied to the main Stage as unstretched, unrotated pixels snapped to the nearest pixel boundaries. Pixels are mapped one to one with the parent object. If the bounds of the bitmap change, the bitmap is recreated instead of being stretched.

No internal bitmap is created unless the cacheAsBitmap property is set to true.

After you set a movie clip's cacheAsBitmap property to true, the rendering does not change, however the movie clip performs pixel snapping automatically. The animation speed can be significantly faster, depending on the complexity of the vector content.

The cacheAsBitmap property is automatically set to true whenever you apply a filter to a movie clip (when its filter array is not empty). If a movie clip has a filter applied to it, cacheAsBitmap is reported as true for that movie clip, even if you set the property to false. If you clear all filters for a movie clip, the cacheAsBitmap setting changes to what it was last set to.

In the following cases a movie clip does not use a bitmap even if the cacheAsBitmap property is set to true, and instead renders the movie clip from vector data:

The cacheAsBitmap property is best used with movie clips that have mostly static content and that do not scale and rotate frequently. With such movie clips, cacheAsBitmap can lead to performance increases when the movie clip is translated (when its x and y position is changed).

Example

The following example applies a drop shadow to a movie clip instance. It then traces the value of the cacheAsBitmap property which is set to true when a filter is applied.

import flash.filters.DropShadowFilter;

var container:MovieClip = setUpShape();
trace(container.cacheAsBitmap); // false
var dropShadow:DropShadowFilter = new DropShadowFilter(6, 45, 0x000000, 50, 5, 5, 1, 2, false, false, false); 
container.filters = new Array(dropShadow);
trace(container.cacheAsBitmap); // true

function setUpShape():MovieClip {
    var mc:MovieClip = this.createEmptyMovieClip("container", this.getNextHighestDepth());
    mc._x = 10;
    mc._y = 10;
    var w:Number = 50;
    var h:Number = 50;
    mc.beginFill(0xFFCC00);
    mc.lineTo(w, 0);
    mc.lineTo(w, h);
    mc.lineTo(0, h);
    mc.lineTo(0, 0);
    mc.endFill();
    return mc;
}

cacheAsBitmap (MovieClip.cacheAsBitmap property)

Example

See also