我正在尝试从网站下载图片。我正在使用的代码在图像可用时工作正常。如果图像不可用则会产生问题。如何验证图像的可用性?
代码:
方法1:
WebRequest requestPic = WebRequest.Create(imageUrl);
WebResponse responsePic = requestPic.GetResponse();
Image webImage = Image.FromStream(responsePic.GetResponseStream()); // Error
webImage.Save("D:\\Images\\Book\\" + fileName + ".jpg");
方法2:
WebClient client = new WebClient();
Stream stream = client.OpenRead(imageUrl);
bitmap = new Bitmap(stream); // Error : Parameter is not valid.
stream.Flush();
stream.Close();
client.dispose();
if (bitmap != null)
{
bitmap.Save("D:\\Images\\" + fileName + ".jpg");
}
修改
Stream有以下声明:
Length '((System.Net.ConnectStream)(str)).Length' threw an exception of type 'System.NotSupportedException' long {System.NotSupportedException}
Position '((System.Net.ConnectStream)(str)).Position' threw an exception of type 'System.NotSupportedException' long {System.NotSupportedException}
ReadTimeout 300000 int
WriteTimeout 300000 int
答案 0 :(得分:159)
无需涉及任何图像类,您只需拨打WebClient.DownloadFile
:
string localFilename = @"c:\localpath\tofile.jpg";
using(WebClient client = new WebClient())
{
client.DownloadFile("http://www.example.com/image.jpg", localFilename);
}
<强>更新强>
由于您需要检查文件是否存在并下载文件(如果存在),最好在同一请求中执行此操作。所以这是一个可以做到这一点的方法:
private static void DownloadRemoteImageFile(string uri, string fileName)
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
// Check that the remote file was found. The ContentType
// check is performed since a request for a non-existent
// image file might be redirected to a 404-page, which would
// yield the StatusCode "OK", even though the image was not
// found.
if ((response.StatusCode == HttpStatusCode.OK ||
response.StatusCode == HttpStatusCode.Moved ||
response.StatusCode == HttpStatusCode.Redirect) &&
response.ContentType.StartsWith("image",StringComparison.OrdinalIgnoreCase))
{
// if the remote file was found, download oit
using (Stream inputStream = response.GetResponseStream())
using (Stream outputStream = File.OpenWrite(fileName))
{
byte[] buffer = new byte[4096];
int bytesRead;
do
{
bytesRead = inputStream.Read(buffer, 0, buffer.Length);
outputStream.Write(buffer, 0, bytesRead);
} while (bytesRead != 0);
}
}
}
简而言之,它会对该文件发出请求,验证响应代码是OK
,Moved
还是Redirect
还是之一ContentType
是一张图片。如果这些条件为真,则下载文件。
答案 1 :(得分:26)
我在一个项目中使用了Fredrik的代码,稍作修改,我想分享一下:
private static bool DownloadRemoteImageFile(string uri, string fileName)
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
HttpWebResponse response;
try
{
response = (HttpWebResponse)request.GetResponse();
}
catch (Exception)
{
return false;
}
// Check that the remote file was found. The ContentType
// check is performed since a request for a non-existent
// image file might be redirected to a 404-page, which would
// yield the StatusCode "OK", even though the image was not
// found.
if ((response.StatusCode == HttpStatusCode.OK ||
response.StatusCode == HttpStatusCode.Moved ||
response.StatusCode == HttpStatusCode.Redirect) &&
response.ContentType.StartsWith("image", StringComparison.OrdinalIgnoreCase))
{
// if the remote file was found, download it
using (Stream inputStream = response.GetResponseStream())
using (Stream outputStream = File.OpenWrite(fileName))
{
byte[] buffer = new byte[4096];
int bytesRead;
do
{
bytesRead = inputStream.Read(buffer, 0, buffer.Length);
outputStream.Write(buffer, 0, bytesRead);
} while (bytesRead != 0);
}
return true;
}
else
return false;
}
主要变化是:
答案 2 :(得分:2)
也可以使用DownloadData方法
private byte[] GetImage(string iconPath)
{
using (WebClient client = new WebClient())
{
byte[] pic = client.DownloadData(iconPath);
//string checkPath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments) +@"\1.png";
//File.WriteAllBytes(checkPath, pic);
return pic;
}
}
答案 3 :(得分:0)
从服务器或网站下载图像并将其存储在本地的最佳实践。
WebClient client=new Webclient();
client.DownloadFile("WebSite URL","C:\\....image.jpg");
client.Dispose();
答案 4 :(得分:0)
您可以使用此代码
using (WebClient client = new WebClient()) {
Stream stream = client.OpenRead(imgUrl);
if (stream != null) {
Bitmap bitmap = new Bitmap(stream);
ImageFormat imageFormat = ImageFormat.Jpeg;
if (bitmap.RawFormat.Equals(ImageFormat.Png)) {
imageFormat = ImageFormat.Png;
}
else if (bitmap.RawFormat.Equals(ImageFormat.Bmp)) {
imageFormat = ImageFormat.Bmp;
}
else if (bitmap.RawFormat.Equals(ImageFormat.Gif)) {
imageFormat = ImageFormat.Gif;
}
else if (bitmap.RawFormat.Equals(ImageFormat.Tiff)) {
imageFormat = ImageFormat.Tiff;
}
bitmap.Save(fileName, imageFormat);
stream.Flush();
stream.Close();
client.Dispose();
}
}
可通过以下网址访问项目:github