POST获取PNG转Base64后iPhone无法扫描二维码问题排查

问题背景 #

• 通过POST请求获取PNG格式的Swish预填充二维码，转换为Base64编码后直接在页面展示（避免本地保存文件）
• 该二维码在Android设备上可正常扫描识别，但iPhone设备无法扫描
• 曾尝试调整编码相关设置，无任何效果，一度推测是二维码中心的Swish logo模糊导致识别失败
• 后续验证：原VB.NET代码及Base64转换逻辑本身无问题，使用PHP复现相同流程也得到同样的iPhone扫描失败结果

相关VB.NET代码 #

Public Sub updateSwish()

    Dim getPrice As Integer = 100

    Try
        Dim data As String = "{'format':'png','size':300,'message':{'value':'test','editable':false},'amount':{'value':" + Total.ToString + ",'editable':false},'payee':{'value':'123456789','editable':false}}"
        Dim json As JObject = JObject.Parse(data)

        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12
        Dim s As HttpWebRequest = HttpWebRequest.Create("https://mpc.getswish.net/qrg-swish/api/v1/prefilled")
        Dim enc As UTF8Encoding
        Dim postdata As String
        Dim postdatabytes As Byte()
        enc = New System.Text.UTF8Encoding()
        postdata = json.ToString
        postdatabytes = enc.GetBytes(postdata)
        s.Method = "POST"
        s.ContentType = "application/json"
        s.ContentLength = postdatabytes.Length

        Dim myresponse As HttpWebResponse
        Dim returnval As System.Drawing.Image

        Using stream = s.GetRequestStream()
            stream.Write(postdatabytes, 0, postdatabytes.Length)
        End Using

        Using mStream As New MemoryStream()
            Dim imgByte As Byte()

            myresponse = CType(s.GetResponse(), HttpWebResponse)
            returnval = Image.FromStream(myresponse.GetResponseStream(), True, True)

            returnval.Save(mStream, returnval.RawFormat)
            imgByte = mStream.ToArray()

            Dim base64String As String = Convert.ToBase64String(imgByte, 0, imgByte.Length)
            imgSwish.Src = "data:image/png;base64," & base64String

        End Using

    Catch ex As Exception
        Me.Page.ClientScript.RegisterStartupScript(Me.GetType(), "ex", "alert('" + ex.Message + "');", True)
    End Try

End Sub

解决方法 #

问题根源在于Swish的v1 API生成的二维码存在iPhone扫描兼容性问题，服务商已针对该问题推出了v2版本API。只需将请求的API端点从v1更换为v2即可解决iPhone无法扫描的问题，无需修改原有的Base64转换或图片处理逻辑。

内容的提问来源于stack exchange，提问作者Jimmy