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Learning ActionScript 3.0 by Zevan Rosser, Rich Shupe

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The BitmapData Class

It is also possible to manipulate bitmaps directly through the use of the BitmapData class. The target of the manipulation needn't be an actual bitmap. Just as Flash Player can create a bitmap surface of a display object automatically, you can create such a surface explicitly. Think of this process as working with a screenshot. Whether the display object contains a bitmap or a vector shape is immaterial. You can capture the bitmap data of that object in either case. Let's start by looking at creating bitmap data from scratch and highlighting the difference between bitmap data and a bitmap.

Creating Bitmaps

There are two parts to working with a bitmap. One is the bitmap display object, and the other is the bitmap data. Think of the bitmap display object as the picture you see on stage, and the bitmap data as a detailed description of the number of pixels used, their individual colors and alpha values, and so on. You will find out later in this chapter that it is sometimes advantageous to work with bitmap data without ever actually displaying a bitmap.

In the following example, we want to see the fruit of our labors, so we will work with both elements. The first line of the script creates a new instance of the BitmapData class, populating it with content. The first two parameters sent to the class are the dimensions of the object, 100 × 100 pixels.

Note

The maximum height and width value of a BitmapData object is 2880 pixels. If you specify a larger value for either ...

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