Flash CS3 Documentation

Programming ActionScript 3.0 > Filtering display objects > Basics of filtering display objects

Basics of filtering display objects

Introduction to filtering display objects

One of the ways to add polish to an application is to add simple graphic effects, such as a drop shadow behind a photo to create the illusion of 3-d, or a glow around a button to show that it is active. ActionScript 3.0 includes nine filters that you can apply to any display object or to a BitmapData instance. These range from basic filters, such as the drop shadow and glow filters, to complex filters for creating various effects, such as the displacement map filter and the convolution filter.

Common filtering tasks

The following tasks are things you'll likely want to accomplish using filters in ActionScript:

• Creating a filter
• Applying a filter to a display object
• Applying a filter to the image data in a BitmapData instance
• Removing filters from an object
• Creating various filter effects, such as:
  • Glow
  • Blur
  • Drop shadow
  • Sharpness
  • Displacement
  • Edge detection
  • Embossing
  • and other effects

Important concepts and terms

The following reference list contains important terms that you will encounter in this chapter:

• Bevel: An edge created by lightening pixels on two sides and darkening pixels on the opposite two sides, creating a three-dimensional border effect commonly used for raised or indented buttons and similar graphics.
• Convolution: Distorting pixels in an image by combining each pixel's value with the values of some or all of its neighboring pixels, using various ratios.
• Displacement: Shifting or moving pixels in an image to a new position.
• Matrix: A grid of numbers used to perform certain mathematical calculations by applying the numbers in the grid to various values, then combining the results.

Working through in-chapter examples

While you're working through the chapter, you may want to test the example code listings that are provided. Because this chapter deals with creating and manipulating visual content, testing the code involves running the code and viewing the results in the SWF that's created. Nearly all the examples either create content using the drawing API or load images to which filters are applied.

To test the code in this chapter:

1. Create an empty Flash document.
2. Select a keyframe in the Timeline.
3. Open the Actions panel and copy the code into the Script pane.
4. Run the program using Control > Test Movie.

   You see the results of the code in the SWF file that's created.

Nearly all the example code includes code that creates a bitmap image, so you can just test the code directly without needing to provide any bitmap content. Alternatively you can change the code listings to load your own images and use those in place of the ones in the examples.

Flash CS3