如果图片过大，一般我们展示的时候要允许用户通过鼠标滚轮进行缩放，同时点击可以拖拽移动（类似百度地图那样的操作）。下面通过一个样例进行演示： 

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
			   xmlns:s="library://ns.adobe.com/flex/spark" 
			   xmlns:mx="library://ns.adobe.com/flex/mx"
			   backgroundColor="0x404040"
			   creationComplete="init(event)">
	<fx:Script>
		<![CDATA[
			import mx.events.FlexEvent;
			
			//图片缩放比例
			private var _imgScale:Number = 1;
			//图片坐标
			private var _imgX:Number = 0;
			private var _imgY:Number = 0;
			
			/**
			 * 设置监听
			 */
			protected function init(event:FlexEvent):void
			{
				img.addEventListener(MouseEvent.MOUSE_DOWN, itemMouseDown);
				img.addEventListener(MouseEvent.MOUSE_UP, itemMouseUp);
				img.addEventListener(MouseEvent.ROLL_OUT, itemMouseUp);
				img.addEventListener(MouseEvent.MOUSE_WHEEL, itemMouseWheel);
			}
			
			/**
			 * 鼠标按下开始拖动
			 */
			private function itemMouseDown(event:MouseEvent = null):void{
				var width:int = img.parent.width - img.width*_imgScale;
				var height:int = img.parent.height - img.height*_imgScale;
				img.startDrag(false, new Rectangle(0, 0 , width, height));
			}
			
			/**
			 * 鼠标弹起停止 拖动
			 */
			private function itemMouseUp(event:MouseEvent):void{
				img.stopDrag();
			}
			
			/**
			 * 鼠标滚轮控制缩放
			 */
			private function itemMouseWheel(event:MouseEvent):void{	
				//计算每次的缩放比例
				_imgScale = this.img.scaleX + (Math.abs(event.delta)/event.delta)*0.05;
				//设置最大最小的缩放限度
				_imgScale = Math.min(1,_imgScale);	
				var minScale:Number = Math.min(img.parent.width/img.width,img.parent.height/img.height);
				_imgScale = Math.max(minScale,_imgScale);
				
				//计算缩放后图片的坐标（保证缩放中心是鼠标）
				var oldScale:Number = this.img.scaleX;				
				_imgX = this.img.x-(_imgScale/oldScale-1)*(this.img.parent.mouseX - this.img.x);
				_imgY = this.img.y-(_imgScale/oldScale-1)*(this.img.parent.mouseY - this.img.y);
				
				//坐标修正
				if(img.width*_imgScale >= img.parent.width){
					if(_imgX>=0){
						_imgX=0;
					}else if((img.width*_imgScale+_imgX)<img.parent.width){
						_imgX=img.parent.width-img.width*_imgScale;
					}
				}
				
				if(img.height*_imgScale >= img.parent.height){
					if(_imgY>=0){
						_imgY=0;
					}else if((img.height*_imgScale+_imgY)<img.parent.height){
						_imgY=img.parent.height-img.height*_imgScale;
					}
				}		
				
				//设置图片缩放比例和坐标 
				this.img.scaleX=_imgScale;
				this.img.scaleY=_imgScale;
				this.img.x = _imgX;
				this.img.y = _imgY;		
			}

		]]>
	</fx:Script>

	<s:Group clipAndEnableScrolling="true" width="70%" height="70%"
			 horizontalCenter="0" verticalCenter="0">
		<s:Rect  width="100%" height="100%">
			<s:fill>
				<s:SolidColor color="0xffffff"/>
			</s:fill>
		</s:Rect>
		<s:Image id="img" source="img.jpg"/>
	</s:Group>
</s:Application>