C# 从 URL 到流的图像
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Image from URL to stream
提问by Cheese
I'm getting images from a url:
我从一个 url 获取图像：
BitmapImage image = new BitmapImage(new Uri(article.ImageURL));
NLBI.Thumbnail.Source = image;
This works perfect, now i need to put it in a stream, to make it into byte array. I'm doing this:
这很完美，现在我需要把它放在一个流中，把它变成字节数组。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();
And code fails with NullReference, how to fix it?
并且代码因 NullReference 而失败，如何解决？
采纳答案by anderZubi
You get a NullReferenceexception because the image is still not loaded when you use it. You can wait to the ImageOpenedevent, and then work with it:
你会得到一个NullReference异常，因为当你使用它时图像仍然没有加载。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;
Other option is to get the stream of the image file directly using WebClient:
其他选项是直接使用 WebClient 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));
回答by Ashok Damani
var webClient = new WebClient();
byte[] imageBytes = webClient.DownloadData(article.ImageURL);
回答by Matsteel
you can use this:
你可以使用这个：
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();
}
