[Casimiro Noteví]

Algo así:

Código Delphi [-]
function EncodeFile(const FileName: string): AnsiString;
var
  stream: TMemoryStream;
begin
  stream := TMemoryStream.Create;
  try
    stream.LoadFromFile(Filename);
    result := EncodeBase64(stream.Memory, stream.Size);
  finally
    stream.Free;
  end;
end;