var center = new CIVector(100, 100); // Default [150 150]
var radGradient = new CIRadialGradient()
{
	Center = center,
	Radius0 = 10F, // Default 5
	Radius1 = 150F, // Default 100
	Color0 = new CIColor(new CGColor(0, 255F, 0)), // Green
	Color1 = new CIColor(new CGColor(0, 0, 0)) // Black
};

// The Generator Filters need to be cropped before they can be displayed
var crop = new CICrop (IUCrop () 
		   { 
			   Image = radGradient.OutputImage,
			   // Create the Bounds based on the Size of the application Window. (UIWindow)
			   Rectangle = new CIVector (0, 0, window.Bounds.Width, window.Bounds.Height) 
		   };		

// Get the Gradient image from the crop filter.
var output = crop.OutputImage;
	
// To render the results, we need to create a context, and then
// use one of the context rendering APIs, in this case, we render the
// result into a CoreGraphics image, which is merely a useful representation
//
var context = CIContext.FromOptions (null);

var cgimage = context.CreateCGImage (output, output.Extent);

// The above cgimage can be added to a screen view, for example, this
// would add it to a UIImageView on the screen:
myImageView.Image = UIImage.FromImage (cgimage);