From: "Lemke" <lemke@gfai.de>
Subject: decoding /encoding of Jpeg-Files with TJPEG
Date: 03 Mar 2000 00:00:00 GMT
Message-ID: <38bf847f@dnews>
Sender: "Lemke" <lemke@gfai.de>
X-Trace: 3 Mar 2000 01:23:11 -0800, 207.105.83.65
Reply-To: "Lemke" <lemke@gfai.de>
Newsgroups: borland.public.delphi.graphics
X-User-Info: 141.16.180.132 141.16.180.132


I need to read an JpegFile and save it with an changed quality to the disk again. I already find out that I have to assign the jpeg-data to an TBimap-Component and then assigned it back to the TJpeg-Component to save it again with an new Quality. If I do this there is an strange behavior.  Problem ist that it works with smal images but if I use larger images (e.g. more than 1 Mb  Jpeg-Files) I get some times an Jpeg-Error number 36 but some times not. Is there anybode with know I can solve this problem. next the code I have written:


var
 JPEGImageS: TJPEGImage;
 BMPImage:  TBitmap;

procedure TForm1.FormCreate(Sender: TObject);
begin
 BMPImage:=  TBitmap.Create;

end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
 BMPImage.Free;
end;

procedure TForm1.Button1Click(Sender: TObject);
var JPEGImageS: TJPEGImage;

begin
   if OpenDialog1.Execute then
   begin
    JPEGImageS:=  TJPEGImage.Create;
    with JPEGImageS do
    begin
       LoadFromFile(OpenDialog1.Filename);
       BMPImage.Width := Width;
       BMPImage.Height := Height;
       BMPImage.Canvas.Draw(0,0,JPEGImageS);
    end;
    JPEGImageS.free
   end;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin

  with TJPEGImage.Create do
  begin
    Assign(BMPImage);
    CompressionQuality:= Trackbar1.Position;
    Compress;
    SaveToFile('d:\Test.jpg');
    Free;
  end;

end;