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function ResizeJPG(FileName: String; NewFileName: String; NewWidth, NewHeight: Integer): String;
var RBit, Bit: TBitmap;
    JPG: TJPEGImage;
begin
  Bit:=TBitmap.Create;
  RBit:=TBitmap.Create;
  JPG:=TJPEGImage.Create;
  JPG.LoadFromFile(FileName);
  Bit.Assign(JPG);       {### hier Fehlermeldung ###}
  RBit.Width:=NewWidth;
  RBit.Height:=NewHeight;
  RBit.Canvas.StretchDraw(Rect(0,0,NewWidth,NewHeight),Bit);
  JPG.Assign(RBit);
  JPG.SaveToFile(FileName);
  JPG.Free;
  RBit.Free;
  Bit.Free;
  Result := 'OK';
end;					

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Procedure JPG_Bildformat_aendern_speichern(FileName: String; NewFileName: String; NewWidth, NewHeight: Integer);
var BMP: TBitmap;
    JPEG: TJPEGImage;
begin
  JPEG:=TJPEGImage.Create;
  JPEG.LoadFromFile(FileName);


  BMP:=TBitmap.Create;
  BMP.Height := NewHeight;
  BMP.Width  := NewWidth;

  BMP.Canvas.StretchDraw(Rect(0,0,BMP.Width,BMP.Height),JPEG);
  JPEG.Assign(BMP);

  JPEG.SaveToFile(NewFileName);
  JPEG.Free;
  BMP.Free;

end;