一个图象转换的问题(100分)

请问如何通过流来将Jpeg图象转换成BitMap,急！！！！最好有完整代码！！

var
MyStream:TMemoryStream;
MyBitMap:TBitMap;
MyJpeg:TJpegImage;

MyJpeg:=TJpegimage.Create;
Mystream :=TMemoryStream.Create;
MyBitMap:=TBitMap.create;
try
QueryImage.savetostream(MyStream);
MyStream.Seek(0,soFromBeginning);
Myjpeg.loadfromstream(MyStream);
MyBitMap.Assign(MyJpeg);
//.....
.....
finally
MyJpeg.Free;
MyStream.Free;
MyBitMap.Free;
end;

慢了。

接受答案了.