Question

我正在尝试创建一个函数，该函数允许我的应用向互联网URL上的图像分配image.Source。在下载图像本身之前，我还需要下载BitmapFrame以获得图像的尺寸详细信息。

问题是我的代码的bFrame.DownloadCompleted部分没有用某些图像触发，所以我需要知道为什么下载事件没有一直触发，以及如何解决它适用于每张图像。

这是我的代码：

private static void GetWebImage(Image image, string path)
    {
        // Adjust image size to the source image's dimensions.
        var bFrame = BitmapFrame.Create(new Uri(path), BitmapCreateOptions.None, BitmapCacheOption.None);
        if (bFrame.IsDownloading)
        {
            bFrame.DownloadCompleted += (e, arg) =>
            {
                image.Width = bFrame.PixelWidth;
                image.Height = bFrame.PixelHeight;

                // Check whether the bitmap is in portrait orientation.
                bool portrait = false;
                if (image.Height > image.Width) { portrait = true; }

                // Resize large images to the correct proportions.
                double shrinkRatio = 0;
                if (portrait && image.Height > 300)
                {
                    shrinkRatio = 300 / image.Height;
                    image.Height = image.Height * shrinkRatio;
                    image.Width = image.Width * shrinkRatio;
                }
                else if (!portrait && image.Width > 400)
                {
                    shrinkRatio = 400 / image.Width;
                    image.Height = image.Height * shrinkRatio;
                    image.Width = image.Width * shrinkRatio;
                }

                // Round the edges of the image.
                image.Clip = new RectangleGeometry(new Rect(0, 0, image.Width, image.Height), 6, 6);

                // Download the image from the URL.
                BitmapImage bImage = new BitmapImage();
                bImage.BeginInit();
                bImage.UriSource = new Uri(path, UriKind.Absolute);
                bImage.EndInit();
                image.Source = bImage;
            };
        }


    }

Answer 1

不知道为什么BitmapFrame确实会那样。

但是，您可以将BitmapImage直接分配给image.Source，以强制立即下载图像。

private static void GetWebImage(Image image, string path)
{
    var bitmap = new BitmapImage(new Uri(path));

    if (bitmap.IsDownloading)
    {
        bitmap.DownloadCompleted += (s, e) => AdjustSize(image, bitmap);
    }
    else
    {
        AdjustSize(image, bitmap);
    }

    image.Source = bitmap;
}

private static void AdjustSize(Image image, BitmapSource bitmap)
{
    image.Width = bitmap.PixelWidth;
    image.Height = bitmap.PixelHeight;

    if (image.Height > image.Width)
    {
        if (image.Height > 300)
        {
            image.Width *= 300 / image.Height;
            image.Height = 300;
        }
    }
    else if (image.Width > 400)
    {
        image.Height *= 400 / image.Width;
        image.Width = 400;
    }

    image.Clip = new RectangleGeometry(
        new Rect(0, 0, image.Width, image.Height), 6, 6);
}

为什么我的BitmapFrame每次都不下载？

1 个答案: