stitch Whether the edges of the noise are made to t together, should the noise be tiled. fractalNoise Whether the style of noise should be fractal noise (true) or turbulence (false). The setting slightly alters the noise algorithm to produce a different style of

noise with the same properties. Fractal noise is more continuous, whereas turbulence has more gaps.

channelOptions Which channels noise should be generated into. See the same option of noise(). Optional; defaults to RGB. grayscale Whether or not the noise is grayscale. Optional; defaults to false. offsets An array of Points, one for each octave, that position the layers.

The perlinNoise() method has a ton of options, but a couple of examples illustrate its capabilities. Example 36-15 shows some basic Perlin noise and examines the effect of baseX, baseY, and

EXAMPLE 36-15

package { import flash.display.*; import flash.events.Event; import flash.events.KeyboardEvent; public class ch36ex15 extends Sprite { protected var bmp:BitmapData; protected var octaves:int = 1; public function ch36ex15() { bmp = new BitmapData(stage.stageWidth, stage.stageHeight); var bitmap:Bitmap = new Bitmap(bmp); stage.addChildAt(bitmap, 0); addEventListener(Event.ENTER_FRAME, onEnterFrame); stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyDown); } protected function onKeyDown(event:KeyboardEvent):void { switch (String.fromCharCode(event.charCode)) { case "+": case "=": octaves++; break; case "-": case "_": octaves--; break; } } protected function onEnterFrame(event:Event):void { bmp.perlinNoise(mouseX, mouseY, octaves, 1, false, false); graphics.clear(); graphics.lineStyle(0, 0xffffff, 0.5); graphics.drawRect(0, 0, mouseX, mouseY); } } }

Try running the example. Move the mouse, and you ll update the size of the rectangle used to calculate a single cycle of the noise s rst octave. Use the + and keys to add and remove octaves. Notice that after around 5 octaves, you can t really see additional octaves; also note the impact on refresh rate. In Example 36-16, you see the effect of edge stitching by creating a BitmapData object with Perlin noise and using it as a bitmap ll. Press a key on the keyboard to toggle stitching on and off.

EXAMPLE 36-16

package { import flash.display.*; import flash.events.Event; import flash.events.KeyboardEvent; import flash.events.TimerEvent; [SWF(frameRate="2")] public class ch36ex16 extends Sprite { protected var bmp:BitmapData; protected var stitch:Boolean = false; public function ch36ex16() { bmp = new BitmapData(200, 200); var shape:Shape = new Shape(); shape.graphics.lineStyle(0, 0, 0); shape.graphics.beginBitmapFill(bmp); shape.graphics.drawRect(0, 0, stage.stageWidth, stage.stageHeight); shape.graphics.endFill(); addChild(shape); stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyDown); addEventListener(Event.ENTER_FRAME, onEnterFrame); } protected function onKeyDown(event:KeyboardEvent):void { stitch = !stitch; } private function onEnterFrame(event:Event):void { bmp.perlinNoise(100, 100, 2, Math.random()*1000, stitch, false, 1, true); } } }

Using the offsets parameter to offset individual octaves of Perlin noise can generate interesting effects. For a good example, look ahead to Example 37-13 (http://actionscriptbible.com/ ch37/ex13). In that example, you use Perlin noise to simulate wind rippling a ag. The bigger octaves move more slowly because the prevailing power of the wind uctuates slowly, whereas smaller octaves move faster, pushing small ripples by much faster in addition to the overall motion.

Summary

A bitmap is a grid of colors, one for each pixel. Bitmaps in Flash Player store 32 bits per pixel in four 8-bit channels: alpha, red, green, and blue. With bitmaps, you have total control over what goes on the screen. Use this to write anything from a simple effect to your own graphics engine.

BitmapData stores the bitmap data. It doesn t give you direct access to the pixels in memory,

BitmapData objects can be transparent or discard alpha channel information. Set this with the transparent property. BitmapData objects are xed in size at construction time.

Bitmap data takes up memory. When releasing BitmapData instances, call dispose() on them to manually dispose the internal bitmap data.

Bitmaps may be smoothly interpolated if the Bitmap s smoothing property is set to true. If false, stage quality settings have no effect on their appearance.

You can get the bitmap representation of any display object or composition of display objects by calling draw() on the BitmapData to draw into. Copy regions of bitmaps or channels of those regions with copyPixels() and

copyChannel().

Access single pixels with the [get/set]Pixel[32]() family of methods. You can copy and set regions of or whole bitmaps in memory using a ByteArray or