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;
   
        }
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 /// <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;
            }

        }