ActionScript: The Definitive Guide

Name

MovieClip._alpha Property — opacity of a clip or movie

Availability

Flash 4 and later

Synopsis

mc._alpha

Access

Read/write

Description

The floating-point _alpha property specifies the opacity (or conversely the transparency) of mc as a percentage—0 is completely transparent whereas 100 is completely opaque. Setting the _alpha of mc affects the visual transparency of all clips nested inside mc but does not affect their _alpha properties. That is, if we have a clip, square, that contains another clip, circle, and we set square._alpha to 50, then circle will be 50% transparent on-screen but will have an _alpha of 100.

Usage

Note that setting the _alpha of a movie clip affects the aa property of the object returned by Color.getTransform( ).

Example

ball._alpha = 60;   // Make ball partially transparent
ball._alpha = 0;    // Make ball invisible

The following clip event handler makes a clip more transparent as the mouse moves down on the screen:

onClipEvent(enterFrame) {
  _alpha = 100 - (_root._ymouse / 400) * 100;
}

See Also

The Color Class; MovieClip ._visible