private async void btnSavePng_Click(object sender, RoutedEventArgs e)
{
var bitmap = imageDst.Source as WriteableBitmap;
if (bitmap != null)
{
await bitmap.SaveAsync(ImageDirectories.InApplicationLocal, ImageFormat.Png, "effect_sample");
var bmp = await WriteableBitmapExtensions.LoadAsync(ImageDirectories.InApplicationLocal, ImageFormat.Png, "effect_sample");
}
}