private void WriteHeader(int width, int depth)
        {
            var header       = PpmHeader.GetBase(width, depth);
            var headerString = header.Flag + '\n' +
                               header.Width + " " + header.Depth + '\n' +
                               header.Max + '\n';

            _buffer.Write(Encoding.UTF8.GetBytes(headerString));
        }
        private void ReadHeader()
        {
            var dimensions = _contents[0].Split(' ').Select(int.Parse).ToArray();
            var max        = int.Parse(_contents[1]);

            _header = new PpmHeader
            {
                Flag  = "P6",
                Width = dimensions[0],
                Depth = dimensions[1],
                Max   = max
            };
        }