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  DownLoadInternetFile('http://www.google.de/favicon.ico','test.ico');
  stream:=TStream.Create;
  ico:=TIcon.Create;
  ico.LoadFromFile('test.ico');
  ico.SaveToStream(stream);
  memo1.Lines.Add(IdEncoderMIME1.Encode(stream));                    

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function Base64DecodeFile(ABase64Str: String; AFileName: String): Boolean;
var
  InSize, OutSize: Cardinal;
  PIn, POut: Pointer;
begin
  result:= False;
  // get size of source
  InSize := Length(ABase64Str);
  // calculate size for destination
  PIn := @ABase64Str[1];
  OutSize := CalcDecodedSize(PIn, InSize);
  // prepare string length to fit result data
  with TMemoryStream.Create() do
  try
    SetSize(OutSize);
    POut := Memory;
    // decode !
    if Base64Decode(PIn, InSize, POut) then
    begin
      SaveToFile(AFileName);
      result:= True;
    end;
  finally
    Free;
  end;
end;                    

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function Base64EncodeFile(AFileName: String; var ABase64Str: String): Boolean;
var
  ms: TMemoryStream;
  InSize, OutSize: Cardinal;
  PIn, POut: Pointer;
begin
  result:= False;
  if FileExists(AFileName) then
  begin
    with TMemoryStream.Create() do
    try
      LoadFromFile(AFileName);
      // get size of source
      InSize := Size;
      Position:= 0;
      // calculate size for destination
      OutSize := CalcEncodedSize(InSize);
      SetLength(ABase64Str, OutSize);
      // encode !
      PIn := Memory;
      POut:= @ABase64Str[1];
      Base64Encode(PIn, InSize, POut);
      result:= True;
    finally
      Free;
    end;
  end;
end;                    

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procedure TForm1.Button1Click(Sender: TObject);
var
  s:string;
begin
  Base64EncodeFile('favicon.ico',s);
  memo1.Lines.Add(s);
end;