imageをbyte配列に変換する

        private byte[] ImageToBinary(Image targetImage)
        {
            using (var mem = new MemoryStream())
            {
                mem.Position = 0;
                targetImage.Save(mem, ImageFormat.Bmp);
                byte[] buffer = new byte[mem.Length];
                mem.Position = 0;
                mem.Read(buffer, 0, (int)mem.Length);
                mem.Close();
                return buffer;
            }
        }