如何将图像URL转换为存储文件?

Question

我正在使用Unsplash API来获取图像。当我发送图像请求时，部分答案是图像URL，如下所示：

https://images.unsplash.com/photo-1535159530326-d7bf54bfb24e?ixlib=rb-0.3.5&q=85&fm=jpg&crop=entropy&cs=srgb&ixid=eyJhcHBfaWQiOjM1NDkzfQ&s

我能够将此URL设置为BitmapImage，并使其成为应用程序UI中的图像源。但是我无法下载它以使其成为存储文件。

如何从此类 URL 下载图像和/或使其成为存储文件？

Answer 1

以下代码会将文件下载到本地存储中，然后为您提供可用于设置图像源的 Uri：

private async Task<String> DownloadImage(string url, String fileName)
{
const String imagesSubdirectory = "DownloadedImages";
var rootFolder = await ApplicationData.Current.LocalFolder.CreateFolderAsync(imagesSubdirectory, CreationCollisionOption.OpenIfExists);
var storageFile = await rootFolder.CreateFileAsync(fileName, CreationCollisionOption.ReplaceExisting);
using (HttpClient client = new HttpClient())
{
byte[] buffer = await client.GetByteArrayAsync(url);
using (Stream stream = await storageFile.OpenStreamForWriteAsync())
stream.Write(buffer, 0, buffer.Length);
}
// Use this path to load image
String newPath = String.Format("ms-appdata:///local/{0}/{1}", imagesSubdirectory, fileName);
return newPath;
}
// Here is an example of how to use the new DownloadImage() method
private async void Button_Download(object sender, RoutedEventArgs e)
{
var uniqueFileName = $@"{Guid.NewGuid()}.jpg";
String newPath = await DownloadImage("https://images.unsplash.com/photo-1535159530326-d7bf54bfb24e?ixlib=rb-0.3.5&q=85&fm=jpg&crop=entropy&cs=srgb&ixid=eyJhcHBfaWQiOjM1NDkzfQ&s=6dbf8e03a25f469d0f845992e6b2eb9e",
uniqueFileName);
myImage.Source = new BitmapImage(new Uri(newPath));
}