Dynamic masking using the drawing API

Dynamic masking using the drawing API

Flash is a much more mature beast than it was years ago and certainly the introduction of the drawing API has helped establish this. Macromedia has included functions for drawing dynamically on stage since the introduction of MX. If you've tried using these functions you've certainly found that although deceptively simple they can be quite effective for creating components and advanced effects.

One of the neatest things you can do with the drawing API is use it to draw dynamic masks. This allows you to create effects that would otherwise been a pain with static masking. In this tutorial I'll give you an overview of the way the drawing API works in connection with dynamic masks with three complete real-world examples. I'm sure you will be impressed by the simplicity and flexibility of this set of tools.

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How to use the drawing API and dynamic masks

The drawing API consists of these 8 functions:

MovieClip.beginFill
MovieClip.beginGradientFill
MovieClip.clear 
MovieClip.curveTo
MovieClip.endFill
MovieClip.lineStyle
MovieClip.lineTo
MovieClip.moveTo 

That's it. In our particular case we won't even need all of these. In the following we will use beginFill, clear, endFill, lineTo and moveTo. In addition we will need the with keyword and createEmptyMovieClip. Let's write a simple script that draws a square on stage:

this.createEmptyMovieClip('square',0);
with(_root.square)
{
  moveTo(0,0);
  beginFill(0x000088)
  lineTo(100,0);
  lineTo(100,100);
  lineTo(0,100);
  endFill();
}