c# - 图片从URL到流

我正在从URL获取图像:

BitmapImage image = new BitmapImage(new Uri(article.ImageURL));
NLBI.Thumbnail.Source = image;

这工作完美，现在我需要将其放入流中，以使其成为字节数组。我正在这样做:

WriteableBitmap wb = new WriteableBitmap(image);
MemoryStream ms = new MemoryStream();
wb.SaveJpeg(ms, image.PixelWidth, image.PixelHeight, 0, 100);
byte[] imageBytes = ms.ToArray();

并且NullReference代码失败，如何解决？

最佳答案

您会收到NullReference异常，因为使用该图像时仍未加载该图像。您可以等待ImageOpened事件，然后使用它:

var image = new BitmapImage(new Uri(article.ImageURL));
image.ImageOpened += (s, e) =>
    {
        image.CreateOptions = BitmapCreateOptions.None;
        WriteableBitmap wb = new WriteableBitmap(image);
        MemoryStream ms = new MemoryStream();
        wb.SaveJpeg(ms, image.PixelWidth, image.PixelHeight, 0, 100);
        byte[] imageBytes = ms.ToArray();
    };
NLBI.Thumbnail.Source = image;

另一个选择是使用WebClient直接获取图像文件的流:

WebClient client = new WebClient();
client.OpenReadCompleted += (s, e) =>
     {
         byte[] imageBytes = new byte[e.Result.Length];
         e.Result.Read(imageBytes, 0, imageBytes.Length);

         // Now you can use the returned stream to set the image source too
         var image = new BitmapImage();
         image.SetSource(e.Result);
         NLBI.Thumbnail.Source = image;
     };
client.OpenReadAsync(new Uri(article.ImageURL));

关于c# - 图片从URL到流，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/17876015/