如果URL链接末尾没有图片格式，是否有办法在C#中直接从URL下载图像？ URL示例：
https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-xpf1/v/t34.0-12/10555140_10201501435212873_1318258071_n.jpg?oh=97ebc03895b7acee9aebbde7d6b002bf&oe=53C9ABB0&__gda__=1405685729_110e04e71d969d392b63b27ec4f4b24a
当 URL 以图片格式结尾时，我知道如何下载该图片。例如：
http://img1.wikia.nocookie.net/__cb20101219155130/uncyclopedia/images/7/70/Facebooklogin.png
简单来说，您可以使用以下方法。
using (WebClient client = new WebClient())
{
client.DownloadFile(new Uri(url), @"c:\temp\image35.png");
// OR
client.DownloadFileAsync(new Uri(url), @"c:\temp\image35.png");
}
这些方法几乎与DownloadString(..)和DownloadStringAsync(...)相同。它们将文件存储在目录中，而不是在C#字符串中，并且URI中不需要格式扩展名。
public void SaveImage(string imageUrl, string filename, ImageFormat format)
{
WebClient client = new WebClient();
Stream stream = client.OpenRead(imageUrl);
Bitmap bitmap; bitmap = new Bitmap(stream);
if (bitmap != null)
{
bitmap.Save(filename, format);
}
stream.Flush();
stream.Close();
client.Dispose();
}
try
{
SaveImage("--- Any Image URL---", "--- Any Image Path ---", ImageFormat.Png)
}
catch(ExternalException)
{
// Something is wrong with Format -- Maybe required Format is not
// applicable here
}
catch(ArgumentNullException)
{
// Something wrong with Stream
}
根据您是否知道图像格式，以下是您可以执行的方式：
using (WebClient webClient = new WebClient())
{
webClient.DownloadFile("http://yoururl.com/image.png", "image.png") ;
}
您可以使用Image.FromStream加载任意类型的通用位图（如jpg、png、bmp、gif等），它会自动检测文件类型，您甚至不需要检查url扩展名(这不是一个很好的做法)。示例：
using (WebClient webClient = new WebClient())
{
byte [] data = webClient.DownloadData("https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-xpf1/v/t34.0-12/10555140_10201501435212873_1318258071_n.jpg?oh=97ebc03895b7acee9aebbde7d6b002bf&oe=53C9ABB0&__gda__=1405685729_110e04e71d9");
using (MemoryStream mem = new MemoryStream(data))
{
using (var yourImage = Image.FromStream(mem))
{
// If you want it as Png
yourImage.Save("path_to_your_file.png", ImageFormat.Png) ;
// If you want it as Jpeg
yourImage.Save("path_to_your_file.jpg", ImageFormat.Jpeg) ;
}
}
}
注意：如果下载的内容不是已知的图片类型，则Image.FromStream可能会抛出ArgumentException异常。
请查看MSDN上此参考资料以查找所有可用格式。这里有关于WebClient和Bitmap的参考信息。
webClient.ResponseHeaders["Content-Type"]，而不是要求图像库检测图像格式。 - bikeman868.NET多年来发生了一些变化，因此本帖中的其他答案已经有些过时：
System.Drawing中的Image（在.NET Core中不可用）来查找图像格式我们不建议您在新开发中使用
WebClient类。 相反，请使用System.Net.Http.HttpClient类。
获取文件扩展名的第一步是从URL中删除所有不必要的部分。我们可以使用Uri.GetLeftPart()和UriPartial.Path，从Scheme到Path获取所有内容。
换句话说，https://www.example.com/image.png?query&with.dots 变成了 https://www.example.com/image.png。
之后，我们可以使用Path.GetExtension()仅获取扩展名（在我的上一个示例中，.png）。
var uriWithoutQuery = uri.GetLeftPart(UriPartial.Path);
var fileExtension = Path.GetExtension(uriWithoutQuery);
接下来应该很简单。使用HttpClient.GetByteArrayAsync下载镜像，创建路径，确保目录存在，然后使用File.WriteAllBytesAsync()将字节写入路径。
private async Task DownloadImageAsync(string directoryPath, string fileName, Uri uri)
{
using var httpClient = new HttpClient();
// Get the file extension
var uriWithoutQuery = uri.GetLeftPart(UriPartial.Path);
var fileExtension = Path.GetExtension(uriWithoutQuery);
// Create file path and ensure directory exists
var path = Path.Combine(directoryPath, $"{fileName}{fileExtension}");
Directory.CreateDirectory(directoryPath);
// Download the image and write to the file
var imageBytes = await httpClient.GetByteArrayAsync(uri);
await File.WriteAllBytesAsync(path, imageBytes);
}
using System;
using System.IO;
using System.Threading.Tasks;
using System.Net.Http;
var folder = "images";
var fileName = "test";
var url = "https://cdn.discordapp.com/attachments/458291463663386646/592779619212460054/Screenshot_20190624-201411.jpg?query&with.dots";
await DownloadImageAsync(folder, fileName, new Uri(url));
HttpClient是不好的做法。它应该在整个应用程序中被重复使用。我写了一个简短的示例ImageDownloader(50行)，附有更多文档，正确地重用HttpClient并正确处理其释放问题，您可以在这里找到。DownloadImageAsync 中，底部的那一行应该是 await httpClient 而不是 await _httpClient，请检查一下。 - Matt Welke对于任何想要下载图像但又不想保存到文件中的人：
Image DownloadImage(string fromUrl)
{
using (System.Net.WebClient webClient = new System.Net.WebClient())
{
using (Stream stream = webClient.OpenRead(fromUrl))
{
return Image.FromStream(stream);
}
}
}
.NET Framework允许PictureBox控件从URL加载图像
并在加载完成事件中保存图像
protected void LoadImage() {
pictureBox1.ImageLocation = "PROXY_URL;}
void pictureBox1_LoadCompleted(object sender, AsyncCompletedEventArgs e) {
pictureBox1.Image.Save(destination); }
大家都为这个问题提供了很好的解决方案，但是所有人提供的解决方案背后存在一个主要问题，即如果图像托管在https上，则不会创建SSL/TLS安全通道。那么我们该怎么办呢？答案很简单，在创建WebClient请求之前添加这两行代码即可。
ServicePointManager.Expect100Continue = true;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
private static void DownloadImage(string url, string saveFilename)
{
var httpWebRequest = (HttpWebRequest)WebRequest.Create(url);
// we need the user agent and default credentials if not,
// we get a forbidden request 303 error, which pretty much means the server thinks we are a bot -- which we are.... hehehehehehe
httpWebRequest.UserAgent = "Case Banana"; // note -- this string can be anything you like, I recommend making it atleast 10 characters
httpWebRequest.UseDefaultCredentials = true;
var httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse();
if ((httpWebResponse.StatusCode != HttpStatusCode.OK &&
httpWebResponse.StatusCode != HttpStatusCode.Moved &&
httpWebResponse.StatusCode != HttpStatusCode.Redirect)
|| !httpWebResponse.ContentType.StartsWith("image", StringComparison.OrdinalIgnoreCase))
{
return;
}
using (var stream = httpWebResponse.GetResponseStream())
{
using (var fileStream = File.OpenWrite(saveFilename))
{
var bytes = new byte[4096];
var read = 0;
do
{
if (stream == null)
{
continue;
}
read = stream.Read(bytes, 0, bytes.Length);
fileStream.Write(bytes, 0, read);
} while (read != 0);
}
}
}
我发现大多数帖子在第二次迭代后都会超时，特别是当你像我一样循环遍历一堆图片时。因此，为了改进上面的建议，这里提供整个方法：
public System.Drawing.Image DownloadImage(string imageUrl)
{
System.Drawing.Image image = null;
try
{
System.Net.HttpWebRequest webRequest = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(imageUrl);
webRequest.AllowWriteStreamBuffering = true;
webRequest.Timeout = 30000;
webRequest.ServicePoint.ConnectionLeaseTimeout = 5000;
webRequest.ServicePoint.MaxIdleTime = 5000;
using (System.Net.WebResponse webResponse = webRequest.GetResponse())
{
using (System.IO.Stream stream = webResponse.GetResponseStream())
{
image = System.Drawing.Image.FromStream(stream);
}
}
webRequest.ServicePoint.CloseConnectionGroup(webRequest.ConnectionGroupName);
webRequest = null;
}
catch (Exception ex)
{
throw new Exception(ex.Message, ex);
}
return image;
}
public class DemoController: Controller
public async Task<FileStreamResult> GetLogoImage(string logoimage)
{
string str = "" ;
var filePath = Server.MapPath("~/App_Data/" + SubfolderName);//If subfolder exist otherwise leave.
// DirectoryInfo dir = new DirectoryInfo(filePath);
string[] filePaths = Directory.GetFiles(@filePath, "*.*");
foreach (var fileTemp in filePaths)
{
str= fileTemp.ToString();
}
return File(new MemoryStream(System.IO.File.ReadAllBytes(str)), System.Web.MimeMapping.GetMimeMapping(str), Path.GetFileName(str));
}
<div><a href="/DemoController/GetLogoImage?Type=Logo" target="_blank">Download Logo</a></div>
私有 void ocmLoadImage_Click(object sender, EventArgs e)
{
字符串 tPathImage;
尝试
{
tPathImage = "https://xxxxx";
WebClient oClient = new WebClient();
Stream oStream = oClient .OpenRead(tPathImage);
Bitmap oBitmap = new Bitmap(oStream );
如果 (oBitmap != null)
{
oBitmap.Save(@"D:\Logo\nick0002.Png", ImageFormat.Png);}
oStream.Flush();
oStream.Close();
oClient.Dispose();
}
捕获异常(Exception oEx)
{
MessageBox.Show(oEx.Message);
}
}