Question

有什么示例我可以从谷歌搜索和下载随机图像吗？使用随机搜索字符串？

我想将此图像用作隐写图像，我希望它是随机图像。

我在Visual Studio 2012中使用C＃。

Answer 1

您可能不想要随机搜索字符串。你可能想要随机主题。这里有一些代码可以帮到你。首先，创建一个主题列表：

private readonly List<string> _topics = new List<string> {"dog", "car", "truck", "cat", "florida"};

当然，您可以随意更改，添加和删除任意数量的主题。接下来，我们将创建一个函数来从Google图像搜索中检索HTML代码，随机选择我们要搜索的主题之一：

private string GetHtmlCode()
{
    var rnd = new Random();

    int topic = rnd.Next(0, _topics.Count - 1);

    string url = "https://www.google.com/search?q=" + _topics[topic] + "&tbm=isch";
    string data = "";

    var request = (HttpWebRequest)WebRequest.Create(url);
    var response = (HttpWebResponse)request.GetResponse();

    using (Stream dataStream = response.GetResponseStream())
    {
        if (dataStream == null)
            return "";
        using (var sr = new StreamReader(dataStream))
        {
            data = sr.ReadToEnd();
        }
    }
    return data;
}

获得HTML代码后，我们需要解析img表下方的images_table标记，并将图片的网址存储在列表中：

private List<string> GetUrls(string html)
{
    var urls = new List<string>();
    int ndx = html.IndexOf("class=\"images_table\"", StringComparison.Ordinal);
    ndx = html.IndexOf("<img", ndx, StringComparison.Ordinal);

    while (ndx >= 0)
    {
        ndx = html.IndexOf("src=\"", ndx, StringComparison.Ordinal);
        ndx = ndx + 5;
        int ndx2 = html.IndexOf("\"", ndx, StringComparison.Ordinal);
        string url = html.Substring(ndx, ndx2 - ndx);
        urls.Add(url);
        ndx = html.IndexOf("<img", ndx, StringComparison.Ordinal);
    }
    return urls;
}

我们需要的最后一个功能是获取一个URL并让它将图像字节下载到一个字节数组中：

private byte[] GetImage(string url)
{
    var request = (HttpWebRequest)WebRequest.Create(url);
    var response = (HttpWebResponse)request.GetResponse();

    using (Stream dataStream = response.GetResponseStream())
    {
        if (dataStream == null)
            return null;
        using (var sr = new BinaryReader(dataStream))
        {
            byte[] bytes = sr.ReadBytes(100000);

            return bytes;
        }
    }

    return null;
}

最后，我们只需将它们结合在一起：

string html = GetHtmlCode();
List<string> urls = GetUrls(html);
var rnd = new Random();

int randomUrl = rnd.Next(0, urls.Count - 1);

string luckyUrl = urls[randomUrl];

byte[] image = GetImage(luckyUrl);
using (var ms = new MemoryStream(image))
{
    pictureBox1.Image = Image.FromStream(ms);
}

<强>更新

我已经收到了一些关于这个答案的请求，要求我修改它以便加载实际的全尺寸图像而不是缩略图。我修改了原始代码，以便现在加载全尺寸图像而不是缩略图。

首先，像以前一样，创建一个主题列表：

private readonly List<string> _topics = new List<string> { "dog", "car", "truck", "cat", "florida" };

当然，您可以随意更改，添加和删除任意数量的主题。接下来，我们将创建一个函数来从Google图像搜索中检索HTML代码，随机选择我们要搜索的主题之一。 GetHtmlCode()此处与缩略图版本中的GetHtmlCode()不同，我们必须在请求中添加Accept和UserAgent，否则Google不会向我们提供完整信息尺寸图片网址：

private string GetHtmlCode()
{
    var rnd = new Random();

    int topic = rnd.Next(0, _topics.Count - 1);

    string url = "https://www.google.com/search?q=" + _topics[topic] + "&tbm=isch";
    string data = "";

    var request = (HttpWebRequest)WebRequest.Create(url);
    request.Accept = "text/html, application/xhtml+xml, */*";
    request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko";

    var response = (HttpWebResponse)request.GetResponse();

    using (Stream dataStream = response.GetResponseStream())
    {
        if (dataStream == null)
            return "";
        using (var sr = new StreamReader(dataStream))
        {
            data = sr.ReadToEnd();
        }
    }
    return data;
}

GetUrls()方法也被重写了，因为我们现在得到的HTML代码与我们在“缩略图”版本中返回的HTML代码不同。它仍然从HTML代码中解析出URL：

private List<string> GetUrls(string html)
{
    var urls = new List<string>();

    int ndx = html.IndexOf("\"ou\"", StringComparison.Ordinal);

    while (ndx >= 0)
    {
        ndx = html.IndexOf("\"", ndx + 4, StringComparison.Ordinal);
        ndx++;
        int ndx2 = html.IndexOf("\"", ndx, StringComparison.Ordinal);
        string url = html.Substring(ndx, ndx2 - ndx);
        urls.Add(url);
        ndx = html.IndexOf("\"ou\"", ndx2, StringComparison.Ordinal);
    }
    return urls;
}

我们需要的最后一个功能是获取一个URL，并将图像字节下载到一个字节数组中。此功能只有一个小变化，与“缩略图”版本不同。我们必须更改ReadBytes()中的数字，因为我们的图片现在会更大：

private byte[] GetImage(string url)
{
    var request = (HttpWebRequest)WebRequest.Create(url);
    var response = (HttpWebResponse)request.GetResponse();

    using (Stream dataStream = response.GetResponseStream())
    {
        if (dataStream == null)
            return null;
        using (var sr = new BinaryReader(dataStream))
        {
            byte[] bytes = sr.ReadBytes(100000000);

            return bytes;
        }
    }

    return null;
}

最后，我们只需将它们绑在一起，就像之前一样：

string html = GetHtmlCode();
List<string> urls = GetUrls(html);
var rnd = new Random();

int randomUrl = rnd.Next(0, urls.Count - 1);

string luckyUrl = urls[randomUrl];

byte[] image = GetImage(luckyUrl);
using (var ms = new MemoryStream(image))
{
    pictureBox1.Image = Image.FromStream(ms);
}

Answer 2

Icemanind的答案主要适合我，虽然我不得不改写Geturls：

    private List<string> GetUrls(string html)
    {
        var urls = new List<string>();

        string search = @",""ou"":""(.*?)"",";
        MatchCollection matches = Regex.Matches(html, search);

        foreach (Match match in matches)
        {
            urls.Add(match.Groups[1].Value);
        }

        return urls;
    }

我还必须找到Image.FromStream（source）的WPF替代品：

            byte[] image = GetImage(luckyUrl);

            using (var stream = new MemoryStream(image))
            {
                var bitmap = new BitmapImage();
                bitmap.BeginInit();
                bitmap.StreamSource = stream;
                bitmap.CacheOption = BitmapCacheOption.OnLoad;
                bitmap.EndInit();
                bitmap.Freeze();

                this.img.Source = bitmap;
            }

从Google中选择并下载随机图片

2 个答案: