Question

所以我正在研究一个小应用程序，该应用程序当前将指定图像从硬盘发送到Google的反向图像搜索并处理响应。问题是我得到的反应不是预期的。我已经尽我所能来复制POST请求的结构，我不能为我的生活弄清楚为什么我没有得到我期望的响应。我得到了200响应代码，但HTML输出是某种谷歌错误（按图搜索不可用。请在几个小时后再试一次）。我已经使用Fiddler来确定请求的结构，从我可以看出，除了缺少Cookie标头之外，从我的应用程序生成的结构几乎完全相同（可能就是这样吗？）。如果是这样，我将如何创建一个cookie并将其插入我的请求？

Here's the request made through Google's upload service.

Here's the request made through my app.

这是我的代码：（注意：我确信它可以更加雄辩和有效地编写（例如使用StringBuilder），并且我已经对它进行了很多硬编码，但它应该足以暂时测试基本功能）< / p>

    String^ url = "https://www.google.com/searchbyimage/upload";
    HttpWebRequest^ request = (HttpWebRequest^) WebRequest::Create(url);
    request->Method = "POST";
    request->UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:16.0) Gecko/20100101 Firefox/16.0";
    request->Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
    request->Headers["Accept-Language"] = "en-US,en;q=0.5";
    request->Headers["Accept-Encoding"] = "gzip, deflate";
    String^ boundary = "-----------------------------23281168279961";
    request->ContentType = "multipart/form-data; boundary=" + boundary;
    request->Referer = "https://www.google.com/imghp?hl=en&tab=wi";

    String^ header = boundary + "\n";
    header += "Content-Disposition: form-data; name=\"image_url\"\n\n\n";

    header += boundary + "\n";
    header += "Content-Disposition: form-data; name=\"encoded_image\"; filename=\"2010-04-09-ec52529.png\"\n";
    header += "Content-Type: image/png\n\n";

    String^ footer = "\n" + boundary + "\n";
    footer += "Content-Disposition: form-data; name=\"image_content\"\n\n\n";

    footer += boundary + "\n";
    footer += "Content-Disposition: form-data; name=\"filename\"\n\n\n";

    footer += boundary + "\n";
    footer += "Content-Disposition: form-data; name=\"num\"\n\n";
    footer += "10\n";

    footer += boundary + "\n";
    footer += "Content-Disposition: form-data; name=\"hl\"\n\n";
    footer += "en\n";

    footer += boundary + "\n";
    footer += "Content-Disposition: form-data; name=\"safe\"\n\n";
    footer += "off\n";

    footer += boundary + "\n";
    footer += "Content-Disposition: form-data; name=\"bih\"\n\n";
    footer += "578\n";

    footer += boundary + "\n";
    footer += "Content-Disposition: form-data; name=\"biw\"\n\n";
    footer += "1366\n";
    footer += boundary + "--\n";

    array<Byte>^ headerData = Encoding::ASCII->GetBytes(header);
    array<Byte>^ imageData = File::ReadAllBytes(oldImage);
    array<Byte>^ footerData = Encoding::ASCII->GetBytes(footer);

    request->ContentLength = headerData->Length + imageData->Length + footerData->Length;

    Stream^ reqStream = request->GetRequestStream();

    reqStream->Write(headerData, 0, headerData->Length);
    reqStream->Write(imageData, 0, imageData->Length);
    reqStream->Write(footerData, 0, footerData->Length);

    HttpWebResponse^ response = (HttpWebResponse^) request->GetResponse();
    StreamReader^ reader = gcnew StreamReader(response->GetResponseStream());
    String^ things = reader->ReadToEnd();

Answer 1

事实证明，Google在处理请求标头时有点挑剔。我遇到了三个问题：

图片以base64编码，+替换为-，/替换为_
Content-Type边界参数不得引用
Content-Disposition名称参数

如果您使用的是C＃，可以使用MultipartFormDataContent处理这些怪癖的替代品，代码改编自here：

public class MultipartFormDataContentCompat : MultipartContent
{
    public MultipartFormDataContentCompat() : base("form-data")
    {
        FixBoundaryParameter();
    }

    public MultipartFormDataContentCompat(string boundary) : base("form-data", boundary)
    {
        FixBoundaryParameter();
    }

    public override void Add(HttpContent content)
    {
        base.Add(content);
        AddContentDisposition(content, null, null);
    }

    public void Add(HttpContent content, string name)
    {
        base.Add(content);
        AddContentDisposition(content, name, null);
    }

    public void Add(HttpContent content, string name, string fileName)
    {
        base.Add(content);
        AddContentDisposition(content, name, fileName);
    }

    private void AddContentDisposition(HttpContent content, string name, string fileName)
    {
        var headers = content.Headers;
        if (headers.ContentDisposition != null)
            return;
        headers.ContentDisposition = new ContentDispositionHeaderValue("form-data")
        {
            Name = QuoteString(name),
            FileName = QuoteString(fileName)
        };
    }

    private string QuoteString(string str)
    {
        return '"' + str + '"';
    }

    private void FixBoundaryParameter()
    {
        var boundary = Headers.ContentType.Parameters.Single(p => p.Name == "boundary");
        boundary.Value = boundary.Value.Trim('"');
    }
}

上传你的图片：

private static string FileToBase64(string imagePath)
{
    byte[] content = File.ReadAllBytes(imagePath);
    string base64 = Convert.ToBase64String(content).Replace('+', '-').Replace('/', '_');
    return base64;
}

public static void UploadImage(string imagePath)
{
    using (var client = new HttpClient())
    {
        var form = new MultipartFormDataContentCompat();
        form.Add(new StringContent(FileToBase64(imagePath)), "image_content");
        form.Add(new StringContent(Path.GetFileName(imagePath)), "filename");
        var response = client.PostAsync("https://images.google.com/searchbyimage/upload", form).Result;
        // Do whatever you want with the response
    }
}

从Multipart Form POST到Google的意外响应

1 个答案: