/// <summary>
/// Creates a temporary image file from a download from a URL
///
/// If you don't pass a file a temporary file is created in Temp Files folder.
/// You're responsible for cleaning up the file after you are done with it.
///
/// You should check the filename that is returned regardless of whether you
/// passed in a filename - if the file is of a different image type the
/// extension may be changed.
/// </summary>
/// <param name="filename">Url of image to download</param>
/// <param name="imageUrl">Optional output image file. Filename may change extension if the image format doesn't match the filename.
/// If not passed a temporary files file is created. Caller is responsible for cleaning up this file.
/// </param>
/// <param name="settings">Optional Http Settings for the request</param>
/// <returns>image filename or null on failure. Note that the filename may have a different extension than the request filename parameter.</returns>
public static string DownloadImageToFile(string imageUrl, string filename = null, HttpRequestSettings settings = null)
{
if (string.IsNullOrEmpty(imageUrl) ||
!imageUrl.StartsWith("http://") && !imageUrl.StartsWith("https://"))
{
return(null);
}
string newFilename;
if (string.IsNullOrEmpty(filename))
{
filename = Path.Combine(Path.GetTempPath(), "~img-" + DataUtils.GenerateUniqueId());
}
filename = Path.ChangeExtension(filename, "bin");
var client = new HttpUtilsWebClient(settings);
try
{
client.DownloadFile(imageUrl, filename);
var ct = client.Response.ContentType; // works
if (string.IsNullOrEmpty(ct) || !ct.StartsWith("image/"))
{
return(null);
}
var ext = ImageUtils.GetExtensionFromMediaType(ct);
if (ext == null)
{
return(null); // invalid image type
}
newFilename = Path.ChangeExtension(filename, ext);
if (File.Exists(newFilename))
{
File.Delete(newFilename);
}
// rename the file
File.Move(filename, newFilename);
}
catch
{
if (File.Exists(filename))
{
File.Delete(filename);
}
return(null);
}
return(newFilename);
}
