我从网址获取图片:
BitmapImage image = new BitmapImage(new Uri(article.ImageURL));
NLBI.Thumbnail.Source = image;
这很完美,现在我需要将它放在一个流中,使其成为字节数组。我这样做:
WriteableBitmap wb = new WriteableBitmap(image);
MemoryStream ms = new MemoryStream();
wb.SaveJpeg(ms, image.PixelWidth, image.PixelHeight, 0, 100);
byte[] imageBytes = ms.ToArray();
代码因NullReference而失败,如何解决?
答案 0 :(得分:28)
var webClient = new WebClient();
byte[] imageBytes = webClient.DownloadData(article.ImageURL);
答案 1 :(得分:15)
您收到NullReference
个异常,因为使用它时图像仍未加载。您可以等到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;
其他选项是使用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));
答案 2 :(得分:0)
你可以用这个:
private async Task<byte[]> GetImageAsByteArray(string urlImage, string urlBase)
{
var client = new HttpClient();
client.BaseAddress = new Uri(urlBase);
var response = await client.GetAsync(urlImage);
return await response.Content.ReadAsByteArrayAsync();
}