在LocalFolder中存储BitmapImage - UWP

我一直在寻找解决方案,但我似乎无法找到任何UWP平台.如何将Bitmap保存到文件？如果更容易使用其他扩展名,则扩展名不必是.jpg.

如果使用WriteableBitmap会更容易.例如,第一种方法是:

public static async Task GetProfilePictureAsync(string userId)
{
    StorageFolder pictureFolder = await ApplicationData.Current.LocalFolder.GetFolderAsync("ProfilePictures");
    StorageFile pictureFile = await pictureFolder.GetFileAsync(userId + ".jpg");

    using (IRandomAccessStream stream = await pictureFile .OpenAsync(FileAccessMode.Read))
    {
        BitmapDecoder decoder = await BitmapDecoder.CreateAsync(stream);
        WriteableBitmap bmp = new WriteableBitmap((int)decoder.PixelWidth, (int)decoder.PixelHeight);

        await bmp.SetSourceAsync(stream);

        return bmp;
    }
}

然后你可以这样做:

public static async Task SaveBitmapToFileAsync(WriteableBitmap image, userId)
{
    StorageFolder pictureFolder = await ApplicationData.Current.LocalFolder.CreateFolderAsync("ProfilePictures",CreationCollisionOption.OpenIfExists);
    var file = await pictureFolder.CreateFileAsync(userId + ".jpg", CreationCollisionOption.ReplaceExisting);

    using (var stream = await file.OpenStreamForWriteAsync())
    {
        BitmapEncoder encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.JpegEncoderId, stream.AsRandomAccessStream());
        var pixelStream = image.PixelBuffer.AsStream();
        byte[] pixels = new byte[bmp.PixelBuffer.Length];

        await pixelStream.ReadAsync(pixels, 0, pixels.Length);

        encoder.SetPixelData(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Ignore, (uint)image.PixelWidth, (uint)image.PixelHeight, 96, 96, pixels);

        await encoder.FlushAsync();
    }
}