C# 图片与Base64码的相互转化问题(代码详解)

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;
      }
    }