C# 图片与Base64的相互转化

　　　　　public ActionResult UploadSignature2(string src_data)
        {
            Class1.Base64StrToImage(src_data, "C:\Users\45448\Desktop\1\"+ DateTime.Now.ToString("yyyyMMddHHss") + ".png");
            return Json(1, JsonRequestBehavior.AllowGet);
        }


        /// <summary>
        /// 将Base64字符串转换为图片并保存到本地
        /// </summary>
        /// <param name="base64Str">base64字符串</param>
        /// <param name="savePath">图片保存地址，如：/Content/Images/10000.png</param>
        /// <returns></returns>
        public static bool Base64StrToImage(string base64Str, string savePath)
        {
            var ret = true;
            try
            {
                base64Str = base64Str.Replace("data:image/png;base64,", "").Replace("data:image/jgp;base64,", "")
                    .Replace("data:image/jpg;base64,", "").Replace("data:image/jpeg;base64,", ""); //将base64头部信息替换
                var bitmap = Base64StrToImage(base64Str);
                if (bitmap != null)
                {
                    //创建文件夹
                    var folderPath = savePath.Substring(0, savePath.LastIndexOf('\'));
                    ////FileHelper.CreateDir(folderPath);
                    if (!Directory.Exists(folderPath))
                    {
                        Directory.CreateDirectory(folderPath);
                    }
                    //图片后缀格式
                    var suffix = savePath.Substring(savePath.LastIndexOf('.') + 1,
                        savePath.Length - savePath.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;

                    //这里复制一份对图像进行保存，否则会出现“GDI+ 中发生一般性错误”的错误提示
                    var bmpNew = new Bitmap(bitmap);
                    bmpNew.Save(savePath, suffixName);
                    bmpNew.Dispose();
                    bitmap.Dispose();
                }
                else
                {
                    ret = false;
                }
            }
            catch (Exception ex)
            {
                ret = false;
            }
            return ret;
   
        }

 /// <summary>
        /// Image 转成 base64
        /// </summary>
        /// <param name="fileFullName"></param>
        public static string ImageToBase64(string fileFullName)
        {
            try
            {
                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();
                return Convert.ToBase64String(arr);
            }
            catch (Exception ex)
            {
                return null;
            }

        }