import flash.utils.getDefinitionByName;
...
var myClass = getDefinitionByName("MyClass") as Class;

import domain.project.MyClass;
...
private var _dummyClass:MyClass;

import domain.project.MyClass;
...
MyClass;

import domain.project.MyClass;
...
[Frame(extraClass="MyClass")]

var myClass = getDefinitionByName("domain.project.MyClass") as Class;

<?xml version="1.0" encoding="utf-8"?>
<project name="floorplanner_as3_core" basedir="." default="build">
  <property name="FLEX_HOME" value="your-flex-sdk-dir-here"/>
  <property name="src.dir" value="src"/>
  <property name="release.dir" value="bin"/>
 
  <taskdef resource="flexTasks.tasks" classpath="${FLEX_HOME}/ant/lib/flexTasks.jar"/> 
 
  <target name="compile">
    <compc output="bin/your-library-project.swc">
      <source-path path-element="${src.dir}" />
      <include-sources dir="${src.dir}" includes="*"/>	
    </compc>
  </target>
 
  <target name="clean">
    <delete>
      <fileset dir="${release.dir}" includes="your-library-project.swc"/>
    </delete>
  </target>
 
  <target name="build" depends="clean, compile" />
 
</project>

var data:ByteArray = fileRef['data'];
var loader:Loader = new Loader();
loader.loadBytes(data);
addChild(loader);

var loader:Loader = new Loader();
loader.contentLoaderInfo.addEventListener(Event.COMPLETE, onDataLoadComplete);
loader.loadBytes(loadFileRef.data);
 
private function onDataLoadComplete(e:Event):void {
  var bitmapData:BitmapData = Bitmap(e.target.content).bitmapData;
  var matrix:Matrix = new Matrix();
  matrix.scale(THUMB_WIDTH/bitmapData.width, THUMB_HEIGHT/bitmapData.height);
 
  imageView.graphics.clear();
  imageView.graphics.beginBitmapFill(bitmapData, matrix, false);
  imageView.graphics.drawRect(0, 0, THUMB_WIDTH, THUMB_HEIGHT);
  imageView.graphics.endFill();
}

var encoder:JPEGEncoder = new JPEGEncoder();
var rawBytes:ByteArray = encoder.encode(bitmapData);
 
var saveFileRef:FileReference = new FileReference();
saveFileRef.save(rawBytes);

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" backgroundGradientColors="[0xFFFFFF,0xFFFFFF]" backgroundColor="0xFFFFFF">
 
	<mx:Script>
		<![CDATA[
			import mx.graphics.codec.JPEGEncoder;
			import mx.binding.utils.BindingUtils;
			import mx.core.UIComponent;
 
			import flash.net.FileReference;
			import flash.net.FileFilter;
			import flash.events.IOErrorEvent;
			import flash.events.Event;
			import flash.utils.ByteArray;
 
			private var loadFileRef:FileReference;
 
			private static const FILE_TYPES:Array = [new FileFilter("Image Files", "*.jpg;*.jpeg;*.gif;*.png;*.JPG;*.JPEG;*.GIF;*.PNG")];
			private static const THUMB_WIDTH:uint = 240;
			private static const THUMB_HEIGHT:uint = 180;
 
			private function loadFile():void {
				loadFileRef = new FileReference();
				loadFileRef.addEventListener(Event.SELECT, onFileSelect);
				loadFileRef.browse();
			}
 
			private function saveFile():void {		
				var bitmapData:BitmapData = new BitmapData(THUMB_WIDTH, THUMB_HEIGHT);
				bitmapData.draw(imageView);
 
				var encoder:JPEGEncoder = new JPEGEncoder();
				var rawBytes:ByteArray = encoder.encode(bitmapData);
 
 				var saveFileRef:FileReference = new FileReference();
				saveFileRef.save(rawBytes);
			}
 
			private function onFileSelect(e:Event):void {
				loadFileRef.addEventListener(Event.COMPLETE, onFileLoadComplete);
				loadFileRef.load();
			}
 
			private function onFileLoadComplete(e:Event):void {
			   	var loader:Loader = new Loader();
			   	loader.contentLoaderInfo.addEventListener(Event.COMPLETE, onDataLoadComplete);
			   	loader.loadBytes(loadFileRef.data);
 
				loadFileRef = null;
			}
 
			private function onDataLoadComplete(e:Event):void {
				var bitmapData:BitmapData = Bitmap(e.target.content).bitmapData;
 
                var matrix:Matrix = new Matrix();
                matrix.scale(THUMB_WIDTH/bitmapData.width, THUMB_HEIGHT/bitmapData.height);
 
				imageView.graphics.clear();
				imageView.graphics.beginBitmapFill(bitmapData, matrix, false); 
				imageView.graphics.drawRect(0, 0, THUMB_WIDTH, THUMB_HEIGHT);
				imageView.graphics.endFill(); 
 
				saveButton.enabled = true;
			}
 
		]]>
	</mx:Script>
	<mx:Panel title="Create thumb image" paddingBottom="5" paddingLeft="5" paddingRight="5" paddingTop="5">
		<mx:VBox>
			<mx:Canvas id="imageView" width="240" height="180" borderThickness="1" borderColor="#CCCCCC" borderStyle="solid"/>
			<mx:HBox paddingTop="5" borderThickness="1">
				<mx:Button label="Load image" click="loadFile()"/>
				<mx:Button label="Save image" click="saveFile()" id="saveButton" enabled="false"/>
			</mx:HBox>
		</mx:VBox>
	</mx:Panel>
</mx:Application>