根据图片路径将图片转换为Base64

public string ImageToBase64(string fileFullName)
        {
            try
            {
                fileFullName = System.AppDomain.CurrentDomain.BaseDirectory.ToString() + fileFullName;
                Bitmap bmp = new Bitmap(fileFullName);
                MemoryStream ms = new MemoryStream();
                var suffix = fileFullName.Substring(fileFullName.LastIndexOf('.') + 1,
                                    fileFullName.Length - fileFullName.LastIndexOf('.') - 1).ToLower();
                var suffixName = suffix == "png"
                                    ? ImageFormat.Png
                                    : suffix == "jpg" || suffix == "jpeg"
                                        ? ImageFormat.Jpeg
                                        : suffix == "bmp"
                                            ? ImageFormat.Bmp
                                            : suffix == "gif"
                                                ? ImageFormat.Gif
                                                : ImageFormat.Jpeg;
                bmp.Save(ms, suffixName);
                byte[] arr = new byte[ms.Length];
                ms.Position = 0;
                ms.Read(arr, 0, (int)ms.Length);
                ms.Close();
                string base64String = "data:image/" + suffix + ";base64," + Convert.ToBase64String(arr);
                return base64String;
            }
            catch (Exception ex)
            {
                return null;
            }
        }