位图保存为流，报Abstract error

Question

procedure TForm1.btnSaveAsClick(Sender: TObject);
var
  aJpg: TJpegImage;
  tsStream: TStream;
begin
  aJpg := TJpegImage.Create;
  tsStream := TStream.Create;
  try
    Image1.Picture.Bitmap.SaveToStream(tsStream);
    aJpg.LoadFromStream(tsStream);
    aJpg.SaveToFile('cc.jpg');
  finally
    aJpg.Free;
    tsStream.Free;
  end;
end;
在“Image1.Picture.Bitmap.SaveToStream(tsStream);”时报错：Abstract error

Answer 1

procedure TForm1.btnSaveAsClick(Sender: TObject);
var
  aJpg: TJpegImage;
  mmStream: TMemoryStream;
begin
  aJpg := TJpegImage.Create;
  mmStream := TMemoryStream.Create;
  try
    mmStream.Position := 0;
    Image1.Picture.Graphic.SaveToStream(mmStream);
    aJpg.LoadFromStream(mmStream);
    aJpg.SaveToFile('cc.jpg');                                                            
  finally
    aJpg.Free;
    mmStream.Free;
  end;
end;可以通过，但保存为的jpg文件大小为0k，且没有图像。怎么回事？谢谢！

Answer 2

将 Image1.Picture.Graphic.SaveToStream(mmStream); 的Graphic改为Bitmap也是不行。

Answer 3

在 aJpg.LoadFromStream(mmStream); 之前加一名句:mmStream.Position := 0;

Answer 4

to toplor:加了，报“Jpeg Error #52”mmStream.Position := 0  在 Image1.Picture.Graphic.SaveToStream(mmStream); 之上没有问题，在它下面就抱错。谢谢！

Answer 5

TStream是个抽像类,不能创建的将TBitmap或TGraphic转换为TJpegImage,就可以保存了,根本用不着用流来转换

Answer 6

procedure TForm1.btnSaveAsClick(Sender: TObject);
var
  aJpg: TJpegImage;
begin
  aJpg := TJpegImage.Create;
  try
    aJpg.Assign(Image1.Picture.Bitmap);
    aJpg.SaveToFile('cc.jpg');
  finally
    aJpg.Free;
  end;
end;