从 url 创建画笔、位图和可写位图

Question

嘿，我有一个使用 silverlight API 的 windows phone 8.1 应用程序。我正在从我的 blob 存储中下载这张图片。

图像来自这样的 link：https://[service].blob.core.windows.net/[imagename].png 并且图像可以在多个浏览器中显示和下载，只需使用 URI。

我现在想将其用作基于 blobstorage 中 imageuri 的画笔：

// If we have a returned SAS.
                BitmapImage myOnlineImage = new BitmapImage();
                myOnlineImage.UriSource = new Uri(uploadImage.ImageUri, UriKind.RelativeOrAbsolute);
                //ImageOnlineTest.Source = myOnlineImage;
                var imageBrush = new ImageBrush
                {
                    ImageSource = myOnlineImage,
                    Stretch = Stretch.None
                };
                var source = FindChildShieldCanvas(CanvasImage, imageBrush);

                WriteableBitmap wbm = new WriteableBitmap((BitmapImage)myOnlineImage);
                ImageOnlineTest.Source = wbm;

myOnlineImage 没有正确创建，至少我不能将图像转换为可写位图图像（从转换中得到一个 null 异常），此外 imagebrush 是空的，即 null。但据我所知这是方法吗？

所以基本上

如何创建基于 url 到 https 站点的 imagebrush？

Answer 1

要从图像创建位图，您必须在设置 URL 之前开始位图对象的初始化。

    BitmapImage myOnlineImage = new BitmapImage();
    myOnlineImage.BeginInit();
    myOnlineImage.UriSource = new Uri(uploadImage.ImageUri, UriKind.RelativeOrAbsolute);
    myOnlineImage.EndInit();

    var imageBrush = new ImageBrush
    {
        ImageSource = myOnlineImage,
        Stretch = Stretch.None
    };
    var source = FindChildShieldCanvas(CanvasImage, imageBrush);

    WriteableBitmap wbm = new WriteableBitmap((BitmapImage)myOnlineImage);
    ImageOnlineTest.Source = wbm;

Answer 2

最后我自己解决了这个问题：

记得加using System.Runtime.InteropServices.WindowsRuntime;

// If we have a returned SAS.
                BitmapImage myOnlineImage = new BitmapImage();

                //myOnlineImage.UriSource = new Uri(uploadImage.ImageUri, UriKind.RelativeOrAbsolute);
                using (var webCLient = new Windows.Web.Http.HttpClient())
                {
                    webCLient.DefaultRequestHeaders.Add("User-Agent", "bot");
                    var responseStream = await webCLient.GetBufferAsync(new Uri(uploadImage.ImageUri, UriKind.RelativeOrAbsolute));
                    var memoryStream = new MemoryStream();//responseStream.ToArrayAsStream().ReadAsync());

                    memoryStream.Write(responseStream.ToArray(), 0, responseStream.ToArray().Length);
                    memoryStream.Position = 0;
                    myOnlineImage.SetSource(memoryStream);

                }
                //ImageOnlineTest.Source = myOnlineImage;
                var imageBrush = new ImageBrush
                {
                    ImageSource = myOnlineImage,
                    Stretch = Stretch.None
                };
                var source = FindChildShieldCanvas(CanvasImage, imageBrush);

                WriteableBitmap wbm = new WriteableBitmap((BitmapImage)myOnlineImage);

此代码适用于 imagebrush 和 writeablebitmap

Answer 3

您可以通过以下方式使用 C# 完成，将适当的代码替换为您的字段。

Rectangle rectangle = new Rectangle();
rectangle.StrokeThickness = 10;
rectangle.Height = 200;
rectangle.Width = 100;
rectangle.SetValue(Canvas.LeftProperty, 100d);
rectangle.SetValue(Canvas.TopProperty, 100d);
rectangle.Fill = new ImageBrush(new BitmapImage(new Uri(@"C:\User\xiaorui.dong\Pictures\profile.jpeg")));

从 url 创建画笔、位图和可写位图

Create imagebrush, bitmap and writeablebitmap from an url

image

azure

windows-phone-8.1

azure-blob-storage

imagebrush