About alpha channel masking

Alpha channel masking is supported if both the mask and the maskee movie clips use bitmap caching. This support also lets you use a filter on the mask independently of the filter that is applied to the maskee itself.

To see an example of alpha masking, download the alpha masking sample file from www.adobe.com/go/learn_fl_samples.

In this sample file, the mask is an oval (oval_mask) that has alpha of 50% and a blur filter applied to it. The maskee (flower_maskee) has alpha of 100% and no filter applied on it. Both movie clips have runtime bitmap caching applied in the Property inspector.

In the Actions panel, the following code is placed on Frame 1 of the Timeline:

flower_maskee.setMask(oval_mask);

When you test the document (Control > Test Movie), the maskee is alpha blended by using the mask.

NOTE

Mask layers do not support alpha channel masking. You must use ActionScript code to apply a mask, and use runtime bitmap caching.

Flash CS3

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