Blur an Image on windows phone

Jun 13, 2014 at 2:01 PM
This code doesn't work
Uri uri = new Uri(AnyUri, UriKind.RelativeOrAbsolute);
BitmapImage img1 = new BitmapImage();
img1.UriSource = uri;
img1.CreateOptions = BitmapCreateOptions.None;
WriteableBitmap wbm = new WriteableBitmap(img1);
var wbm2 = WriteableBitmapExtensions.Convolute(wbm, WriteableBitmapExtensions.KernelGaussianBlur5x5);
PanoramaBackground.ImageSource = wbm2;
It throws an exception of "Object reference not set to an instance of an object" at the line
WriteableBitmap wbm = new WriteableBitmap(img1);
Why ??