自动加载图片类

package
{
    import com.lorentz.SVG.display.SVGDocument;
    import com.lorentz.SVG.events.SVGEvent;
    import com.lorentz.processing.ProcessExecutor;
    
    import flash.display.DisplayObject;
    import flash.display.Loader;
    import flash.display.LoaderInfo;
    import flash.display.Sprite;
    import flash.events.Event;
    import flash.events.IOErrorEvent;
    import flash.net.URLLoader;
    import flash.net.URLLoaderDataFormat;
    import flash.net.URLRequest;
    import flash.utils.ByteArray;
    
    public class LoadImage extends Sprite
    {
        private var _url:String;
        private var _loader:URLLoader;
        private var _byLoader:Loader;
        private var _isNeedAll:Boolean;

        private var _needW:uint;
        private var _needH:uint;
        
        public var data:Object;

        public function LoadImage(needWidth:uint = 0, needHeight:uint = 0, url:String = ‘‘, isNeedAllResize:Boolean = false)
        {
            super();
            
            if(url != ‘‘)        _url = url;
            if(needWidth != 0)    _needW = needWidth;
            if(needHeight != 0)    _needH = needHeight;
            
            _isNeedAll = isNeedAllResize;
            
            _loader = new URLLoader();
            _loader.dataFormat = URLLoaderDataFormat.BINARY;
        }

        public function load(url:String=‘‘):void
        {
            if(url != ‘‘)        _url = url;
            
            if(_url == ‘‘)
            {
                trace("load image error url is null");
                return;
            }

            _loader.addEventListener(Event.COMPLETE, loadCompleteHandler);
            _loader.addEventListener(IOErrorEvent.IO_ERROR, loadErrorHandler);

            try
            {
                _loader.load(new URLRequest(_url));
            } 
            catch(error:Error) 
            {
                trace("load url error");
            }
        }
        
        private function loadCompleteHandler(event:Event):void
        {
            if(_loader == null) return;
            var ba:ByteArray = _loader.data as ByteArray;
            if(ba == null)    return;
            var type:String = getFileType(ba);

            _byLoader = new Loader();
            switch(type)
            {
                case ImageType.BMP:
                case ImageType.GIF:
                case ImageType.PNG:
                case ImageType.JPG:
                {
                    _byLoader.loadBytes(ba);
                    _byLoader.contentLoaderInfo.addEventListener(Event.COMPLETE, byLoadComHandler);
                    break;
                }

                case ImageType.SVG:
                {
                    ProcessExecutor.instance.initialize(stage);

                    var svg:SVGDocument = new SVGDocument();
                    svg.parse(ba.readUTFBytes(ba.length));
                    svg.addEventListener(SVGEvent.RENDERED, 
                        function onRendered(event:SVGEvent):void{
                            resizeDS(event.target as DisplayObject);
                        });
                    addChild(svg);
                    break;
                }
    
                default:
                {
                    break;
                }
            }
            
        }
        
        private function byLoadComHandler(event:Event):void
        {
            var info:LoaderInfo = event.target as LoaderInfo;
            resizeDS(info.content);
            addChild(info.content);

            _loader.removeEventListener(Event.COMPLETE, loadCompleteHandler);
            _loader.removeEventListener(IOErrorEvent.IO_ERROR, loadErrorHandler);
            _byLoader.contentLoaderInfo.removeEventListener(Event.COMPLETE, byLoadComHandler);
        }

        private function getFileType(fileData : ByteArray) : String {
            var b0 : int = fileData.readUnsignedByte();
            var b1 : int = fileData.readUnsignedByte();
            fileData.position = 0;

            if(b0 == 66 && b1 == 77) {
                return ImageType.BMP;
            }else if(b0 == 255 && b1 == 216) {
                return ImageType.JPG;
            }else if(b0 == 137 && b1 == 80) {
                return ImageType.PNG;
            }else if(b0 == 71 && b1 == 73) {
                return ImageType.GIF;
            }else if(b0 == 60 && b1 == 63){
                return ImageType.SVG;
            }

            return ImageType.UNKNOW;
        }
        
        private function loadErrorHandler(event:IOErrorEvent):void
        {
            trace("load image error");
        }
        
        private function resizeDS(ds:DisplayObject):void
        {
            var temp:uint;
            if(_needH != 0){
                temp = ds.height;
                ds.height = _needH;
                if(!_isNeedAll){
                    ds.width = Math.round(ds.height / temp * ds.width);
                }else{
                    ds.width = _needW;
                }
            }else if(_needW != 0){
                temp = ds.width;
                ds.width = _needW;
                if(!_isNeedAll){
                    ds.height = Math.round(ds.width / temp * ds.height);
                }else{
                    ds.height = _needH;
                }

            }
        }
    }
}