Question

I have a jpeg file saved in a string. I would like to load/assign the string to a TImage in Delphi7. I use KOL for the following Code:

var
 ImageStream : PStream;
 ImageString : String;
 MyJpeg      : TJpeg;
begin
 ImageStream:= NewMemoryStream; // Create New Stream.
 ImageStream.Write(ImageString [1], Length(ImageString )); // Fill the stream.
 ImageStream.Position := 0;     // Set Position to 0.
 // ImageStream.SaveToFile('C:\test.jpg', 0, ImageStream.Size); // Debug --> WORKS!
 MyJpeg := TJpegImage.Create; // Create a Jpeg Image. 
 MyJpeg.LoadFromStream(@ImageStream); // ???
 Image1.picture.Assign(MyJpeg);       // No picture is shown
end;

It should work since PStream is just a pointer to TStream…
But there is no picture shown in Timage…
Thanks for your help 🙂

Answer 1

You state that

PStream is just a pointer to TStream

In which case this code

MyJpeg.LoadFromStream(@ImageStream);

cannot work. You are passing, to a parameter of type TStream, a pointer to a pointer to TStream. To make your code compile you need to pass a TStream to LoadFromStream. Like this:

MyJpeg.LoadFromStream(ImageStream^);

---

In your position, I would probably use a TStringStream like this.

var
  Stream: TStringStream;
....
Stream := TStringStream.Create(ImageString);
try
  MyJpeg := TJpegImage.Create;
  try
    MyJpeg.LoadFromStream(Stream);
    Image1.Picture.Assign(MyJpeg);
  finally
    MyJpeg.Free;
  end;
finally
  Stream.Free;
end;

Perhaps there is a KOL way to do that, I don’t know KOL at all.