SpotlightFilter Class

public ref class SpotlightFilter sealed : IFilter, 
	__ISpotlightFilterPublicNonVirtuals

using (var filterEffect = new FilterEffect(source))
{
    // Initialize the filter and add the filter to the FilterEffect collection
    var filter = new SpotlightFilter(new Windows.Foundation.Point(450, 400), 200, 0.5);

    filterEffect.Filters = new IFilter[] { filter };

    // Create a target where the filtered image will be rendered to
    var target = new WriteableBitmap(width, height);

    // Create a new renderer which outputs WriteableBitmaps
    using (var renderer = new WriteableBitmapRenderer(filterEffect, target))
    {
        // Render the image with the filter(s)
        await renderer.RenderAsync();

        // Set the output image to Image control as a source
        ImageControl.Source = target;
    }

    await SaveEffectAsync(filterEffect, "SpotlightFilter.jpg", outputImageSize);
}