从Google中选择并下载随机图片

Question

有没有任何示例我如何从谷歌搜索和下载随机图像？使用随机搜索字符串？

我想用这个图像作为隐写图像,我希望它是一个随机的图像.

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位于images_table表格下方的标记,并将图像的URL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,我们只需将它们组合在一起:

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);
}

UPDATE

我已经得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()这里GetHtmlCode()与缩略图版本的不同之处在于我们必须在请求中添加a Accept和a UserAgent,否则Google将不会向我们提供完整尺寸的图片网址:

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;
}

该GetUrls()方法也被重写,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代码中解析出来的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.我们不得不改变数字,ReadBytes()因为我们的图像现在会更大:

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,我们只需要将它们组合在一起,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);
}