vb.net - 上传图像多部分表单 HTTPWebRequest - 获取图像数据到字符串？

Question

我正在尝试使用 HTTPWebRequest 上传一个包含多个部分的表单，在我添加要上传的图片之前一切正常，主要是我正在尝试执行与浏览器发出的请求完全相同的请求，如下所示:

-----------------------------41184676334
Content-Disposition: form-data; name="file"; filename="guitar tape.jpg"
Content-Type: image/jpeg

IMAGEDATAHERE
-----------------------------41184676334
Content-Disposition: form-data; name="save"

save
-----------------------------41184676334--

我不知道如何格式化/读取图像以将其设置为我在下面提出的请求:

            Dim boundary As String = "-----------------------------" & DateTime.Now.Ticks.ToString("x")
        Dim req As HttpWebRequest = DirectCast(WebRequest.Create("http://www.mysite.com/upload.php"), HttpWebRequest)
        req.Method = "POST"
        req.ContentType = "multipart/form-data; boundary=" & "---------------------------" & DateTime.Now.Ticks.ToString("x")
        req.KeepAlive = False
        Dim builder As New StringBuilder()
        builder.Append(boundary & vbCrLf & "Content-Disposition: form-data; name=""variable1""" & vbCrLf & vbCrLf & "1" & vbCrLf)
        builder.Append(boundary & vbCrLf & "Content-Disposition: form-data; name=""file""; filename=""" & FileName & """" & vbCrLf)
        builder.Append("Content-Type: application/octet-stream")
        builder.Append(vbCrLf & vbCrLf)
        ' Add Photo Here
        If UpdateImage = True Then
            ' Load Image
            Dim ImageData As System.Drawing.Image
            Dim fs As New System.IO.FileStream(ImagePath, System.IO.FileMode.Open)
            ImageData = Image.FromStream(fs)
            fs.Close()
            ' Add Image To Header
            builder.Append(ImageData)
            builder.Append(vbCrLf)
        Else
            builder.Append(vbCrLf)
        End If
        builder.Append(boundary & vbCrLf & "Content-Disposition: form-data; name=""save""" & vbCrLf & vbCrLf & "save")
        ' Footer Bytes
        Dim close As Byte() = Encoding.UTF8.GetBytes("--")
        Dim postHeader As String = builder.ToString()
        Dim postHeaderBytes As Byte() = Encoding.UTF8.GetBytes(postHeader)
        Dim boundaryBytes As Byte() = Encoding.ASCII.GetBytes(vbCrLf & boundary & "--" & vbCrLf)
        Dim length As Long = postHeaderBytes.Length + boundaryBytes.Length
        req.ContentLength = length
        Dim requestStream As Stream = req.GetRequestStream()
        Dim fulllength As Integer = postHeaderBytes.Length + boundaryBytes.Length
        ' Write out our post header
        requestStream.Write(postHeaderBytes, 0, postHeaderBytes.Length)
        ' Write out the trailing boundary
        requestStream.Write(boundaryBytes, 0, boundaryBytes.Length)
        Dim responce As WebResponse
        responce = req.GetResponse()
        requestStream.Close()
        Dim s As Stream = responce.GetResponseStream()
        Dim sr As New StreamReader(s)
        Dim Content As String = sr.ReadToEnd()

目前它只是将“System.Drawing.Bitmap”作为图像数据发布，但我不确定如何为看起来像这样的图像获取相同的原始数据:

    J©õݨe‚Lnž¿Ëã/ǧúÐ5ý¼C÷Cý>ß’t;fm—=Äw:�/E±ËÙÏ$á@%Pc>×    Šgw.²Ab“:ÅÓù:ϯÌh6à€Z§Ó‚g£®hÚD6¨Ø^Ú2ô`ä¨L�YÆÄÅCX#I“ÈÌãj¦L˜•’|¥�Eb¡ëQ–¤Ú, 3\UzL  öÔoj4�•±’u«c¼#„oÕ`îF>·o—ŠûÅ«ÎÑ™¶Ç˜ýº*i°œÈVŒ�Qû”Ñ[.�ÔmçE•ì¦eNCh�Ù
é§�É$m¿ôš"»ÌNæ(VÌmp›F¹XÈ88™ªüµ…d•XµÔÜ#�ˆŠv‘º‚F‚§Yûb

关于我如何做到这一点或者我是否需要改变我的方法有什么想法吗？

Answer 1

    builder.Append(ImageData)

不正确。您需要以字节形式读取图像，然后将字节 [] 添加到多部分帖子中。

详见 Using HttpWebRequest to POST data/upload image using multipart/form-data

并确保使用 http 嗅探器(即 fiddler)来查看它实际发送的内容。

首先，将图像加载到字节数组中，然后将其转换为base64:

imgBase64 = Convert.ToBase64String(my_image_byte_array)