ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Working with bitmaps
Often, when bitmap images are scaled, they become blurred and distorted. To help reduce this distortion, use the
smoothing property of the BitmapData class. This Boolean property, when set to true, smooths, or anti-aliases, the
pixels within the image when it is scaled. This gives the image a clearer and more natural appearance.
Understanding the BitmapData class
Flash Player 9 and later, Adobe AIR 1.0 and later
The BitmapData class, which is in the flash.display package, can be likened to a photographic snapshot of the pixels
contained within a loaded or dynamically created bitmap image. This snapshot is represented by an array of pixel data
within the object. The BitmapData class also contains a series of built-in methods that are useful for creation and
manipulation of pixel data.
To instantiate a BitmapData object, use the following code:
var myBitmap:BitmapData = new BitmapData(width:Number, height:Number, transparent:Boolean,
fillColor:uinit);
The width and height parameters specify the size of the bitmap. Starting with AIR 3 and Flash player 11, the size
limits for a BitmapData object have been removed. The maximum size of a bitmap is dependent on the operating
system.
In AIR 1.5 and Flash Player 10, the maximum size for a BitmapData object is 8,191 pixels in width or height, and the
total number of pixels cannot exceed 16,777,215 pixels. (So, if a BitmapData object is 8,191 pixels wide, it can only be
2,048 pixels high.) In Flash Player 9 and earlier and AIR 1.1 and earlier, the limitation is 2,880 pixels in height and 2,880
in width.
The transparent parameter specifies whether the bitmap data includes an alpha channel (true) or not (false). The
fillColor parameter is a 32-bit color value that specifies the background color, as well as the transparency value (if
it has been set to true). The following example creates a BitmapData object with an orange background that is 50
percent transparent:
var myBitmap:BitmapData = new BitmapData(150, 150, true, 0x80FF3300);
To render a newly created BitmapData object to the screen, assign it to or wrap it in a Bitmap instance. To do this, you
can either pass the BitmapData object as a parameter of the Bitmap object’s constructor, or you can assign it to the
bitmapData property of an existing Bitmap instance. You must also add the Bitmap instance to the display list by
calling the addChild() or addChildAt() methods of the display object container that will contain the Bitmap
instance. For more information on working with the display list, see “Adding display objects to the display list” on
page 158.
The following example creates a BitmapData object with a red fill, and displays it in a Bitmap instance:
var myBitmapDataObject:BitmapData = new BitmapData(150, 150, false, 0xFF0000);
var myImage:Bitmap = new Bitmap(myBitmapDataObject);
addChild(myImage);
Manipulating pixels
Flash Player 9 and later, Adobe AIR 1.0 and later
The BitmapData class contains a set of methods that allow you to manipulate pixel data values.
Last updated 6/6/2012
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