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JPEG SaveToStream Problem

Posted on 2008-10-05
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Last Modified: 2013-11-05
Can anyone please tell me why this doesn't work.  As a test, after I called LoadFromFile I also loaded the image into a TImage component and it appears just fine.  MyJPEG height and width are correct.  It just doesn't load anything to stream.  Aargh!   Thanks.

var
  ms: TMemoryStream;
  MyJPEG: TJPEGImage;
begin
  ms := TMemoryStream.Create;
  try
    MyJPEG := TJPEGImage.Create;
    try
        MyJPEG.LoadFromFile('image1.jpg');
        MyJPEG.SaveToStream(ms);
        ms.Position := 0;
//ms.memory^ shows "(no value)" and if I try to LoadFromStream() into any image the stream is empty.
    finally
       MyJPEG.Free;
       end;
  finally
     ms.Free;
     end;


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Question by:alexiat
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4 Comments
 
LVL 18

Expert Comment

by:Johnjces
ID: 22645313
try changing your ms.Position := 0 to:

ms..Seek(0, soFromBeginning);

Give that a try.

John
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Accepted Solution

by:
2266180 earned 2000 total points
ID: 22645319
don't blindly trust the debugger. different debugger versions (from different delphi versions) have different small and rare issues with debugging sertain more complex expressions.

instead, use something that you can really rely on. like
ms.savetofile(filename here);

your code works perfectly with this.
uses jpeg;
 
procedure TForm1.FormCreate(Sender: TObject);
var
  ms: TMemoryStream;
  MyJPEG: TJPEGImage;
begin
  ms := TMemoryStream.Create;
  try
    MyJPEG := TJPEGImage.Create;
    try
      MyJPEG.LoadFromFile('d:\test.jpg');
      MyJPEG.SaveToStream(ms);
      ms.Position := 0;
      ms.savetofile('d:\test_mem.jpg');
    finally
      MyJPEG.Free;
    end;
  finally
    ms.Free;
  end;
end;

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LVL 18

Expert Comment

by:Johnjces
ID: 22645320
ms.Seek(0, soFromBeginning).

I double clicked the dot... only one not ms.. but ms.

(I know you know that but I messed up so want to make certain).

John
0
 

Author Closing Comment

by:alexiat
ID: 31503214
Whew. Thanks. Who knew you couldn't trust the debugger.  I guess this means it is the 3rd party component who is trying to use the stream that is having problems with it.  I thought I was blindly missing something.
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