在Metro Windows 8中将ImageSource转换为WriteableBitmap

// 将ImageSource转换为WriteableBitmap
private async Task<WriteableBitmap> ConvertImageSourceToWriteableBitmap(ImageSource imageSource)
{
    WriteableBitmap writeableBitmap = null;
    if (imageSource != null)
    {
        var stream = new InMemoryRandomAccessStream();
        var encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, stream);
        var pixelData = await imageSource.ToPixelDataAsync();
        encoder.SetPixelData(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Ignore, (uint)imageSource.PixelWidth, (uint)imageSource.PixelHeight, 96.0, 96.0, pixelData);
        await encoder.FlushAsync();
        stream.Seek(0);
        var bitmapImage = new BitmapImage();
        bitmapImage.SetSource(stream);
        writeableBitmap = new WriteableBitmap(bitmapImage.PixelWidth, bitmapImage.PixelHeight);
        stream.Seek(0);
        await writeableBitmap.SetSourceAsync(stream);
    }
    return writeableBitmap;
}

public static class ImageSourceExtensions
{
    public static async Task<byte[]> ToPixelDataAsync(this ImageSource imageSource)
    {
        byte[] pixelData = null;
        if (imageSource != null)
        {
            var randomAccessStream = new InMemoryRandomAccessStream();
            var bitmapEncoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, randomAccessStream);
            var softwareBitmap = await imageSource.ToSoftwareBitmapAsync();
            bitmapEncoder.SetSoftwareBitmap(softwareBitmap);
            await bitmapEncoder.FlushAsync();
            pixelData = (await randomAccessStream.ToArrayAsync()).ToArray();
        }
        return pixelData;
    }

    private static async Task<SoftwareBitmap> ToSoftwareBitmapAsync(this ImageSource imageSource)
    {
        SoftwareBitmap softwareBitmap = null;
        if (imageSource is SoftwareBitmapSource softwareBitmapSource)
        {
            softwareBitmap = softwareBitmapSource.SoftwareBitmap;
        }
        else if (imageSource is WriteableBitmap writeableBitmap)
        {
            softwareBitmap = SoftwareBitmap.CreateCopyFromBuffer(writeableBitmap.PixelBuffer, BitmapPixelFormat.Bgra8, writeableBitmap.PixelWidth, writeableBitmap.PixelHeight);
        }
        else if (imageSource is BitmapImage bitmapImage)
        {
            softwareBitmap = await bitmapImage.ToSoftwareBitmapAsync();
        }
        return softwareBitmap;
    }

    private static async Task<SoftwareBitmap> ToSoftwareBitmapAsync(this BitmapImage bitmapImage)
    {
        SoftwareBitmap softwareBitmap = null;
        if (bitmapImage != null)
        {
            var randomAccessStream = new InMemoryRandomAccessStream();
            var bitmapEncoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, randomAccessStream);
            bitmapEncoder.SetPixelData(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Ignore, (uint)bitmapImage.PixelWidth, (uint)bitmapImage.PixelHeight, 96.0, 96.0, await bitmapImage.ToPixelDataAsync());
            await bitmapEncoder.FlushAsync();
            randomAccessStream.Seek(0);
            softwareBitmap = await BitmapDecoder.CreateAsync(randomAccessStream).AsTask().ContinueWith(async (task) =>
            {
                var bitmapDecoder = task.Result;
                return await bitmapDecoder.GetSoftwareBitmapAsync();
            }).Unwrap().ConfigureAwait(false);
        }
        return softwareBitmap;
    }

    private static async Task<byte[]> ToArrayAsync(this IRandomAccessStream randomAccessStream)
    {
        byte[] data = new byte[randomAccessStream.Size];
        await randomAccessStream.ReadAsync(data.AsBuffer(), (uint)randomAccessStream.Size, InputStreamOptions.None);
        return data;
    }
}