ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Working with bitmaps
The following example creates a 150 x 150 pixel BitmapData object that calls the perlinNoise() method to generate
a green and blue cloud effect:
package
{
import flash.display.Sprite;
import flash.display.Bitmap;
import flash.display.BitmapData;
import flash.display.BitmapDataChannel;
}
public class BitmapNoise2 extends Sprite
{
public function BitmapNoise2()
{
var myBitmapDataObject:BitmapData =
new BitmapData(150, 150, false, 0x00FF0000);
}
}
var seed:Number = Math.floor(Math.random() * 100);
var channels:uint = BitmapDataChannel.GREEN | BitmapDataChannel.BLUE
myBitmapDataObject.perlinNoise(100, 80, 6, seed, false, true, channels, false, null);
var myBitmap:Bitmap = new Bitmap(myBitmapDataObject);
addChild(myBitmap);
Scrolling bitmaps
Flash Player 9 and later, Adobe AIR 1.0 and later
Imagine you have created a street mapping application where each time the user moves the map you are required to
update the view (even if the map has been moved by just a few pixels).
One way to create this functionality would be to re-render a new image containing the updated map view each time
the user moves the map. Alternatively, you could create a large single image and use the scroll() method.
The scroll() method copies an on-screen bitmap and then pastes it to a new offset location—specified by (x, y)
parameters. If a portion of the bitmap happens to reside off-stage, this gives the effect that the image has shifted. When
combined with a timer function (or an enterFrame event), you can make the image appear to be animating or
scrolling.
The following example takes the previous perlin noise example and generates a larger bitmap image (three-fourths of
which is rendered off-stage). The scroll() method is then applied, along with an enterFrame event listener that
offsets the image by one pixel in a diagonally downward direction. This method is called each time the frame is entered
and as a result, the off screen portions of the image are rendered to the Stage as the image scrolls down.
Last updated 6/6/2012
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