请教，TStream问题

Question

下面两个Stream有什么不同?
为什么我用第一种方法得不到想要的图片
var
  tmp: TMemoryStream;
begin
  tmp := TMemoryStream.Create;
  Image1.Canvas.LineTo(100,100);
  Image1.Picture.Bitmap.SaveToStream(tmp);//成功
  tmp.SaveToStream('test.bmp');//成功
  Image2.Picture.Bitmap.LoadFromStream(tmp);//不成功,看不到图片无错误提示
end;
而第二种可以？
var
  tmp: TMemoryStream;
begin
  tmp := TMemoryStream.Create; 
  tmp.LoadFromFile('test.bmp');
  Image2.Picture.Bitmap.LoadFromStream(tmp);//成功，可看到图片
end;

Answer 1

tmp.SaveToStream('test.bmp');//造成了流已经到了最后，
你把流位置重新弄到开始处

Answer 2

设定 tmp.Position ：＝ 0 既可
如下：
  tmp := TMemoryStream.Create;
  Image1.Canvas.LineTo(100,100);
  Image1.Picture.Bitmap.SaveToStream(tmp);//成功
  tmp.Position := 0;
  Image2.Picture.Bitmap.LoadFromStream(tmp);//不成功,看不到图片无错误提示
  tmp.Free;

Answer 3

但是我删除tmp.SaveToStream('test.bmp');这一句也一样呀

Answer 4

var
  tmp: TMemoryStream;
begin
  tmp := TMemoryStream.Create;
  Image1.Canvas.LineTo(100,100);
  Image1.Picture.Bitmap.SaveToStream(tmp);//成功
  tmp.SaveToStream('test.bmp');//成功
  tmp.Position := 0;  //加上这句试试!!
  Image2.Picture.Bitmap.LoadFromStream(tmp);//不成功,看不到图片无错误提示
end;

Answer 5

呵呵，可以了，就是少了这句tmp.Postion:=0;谢谢大家 :)

Answer 6

tmp.SaveToStream('test.bmp');
  tmp.Position:=0;//加一句
  Image2.Picture.Bitmap.LoadFromStream(tmp);
再试试方法一看看！