Xamarin.Forms-Samples/FormulaOneApp/FormulaOneApp.WinPhone/Controls/ImageCircleRenderer.cs

using System;
using System.Windows.Media;
using FormulaOneApp.WinPhone.Controls;
using Xamarin.Forms;
using Xamarin.Forms.Platform.WinPhone;

[assembly: ExportRenderer(typeof(FormulaOneApp.Controls.CircleImageAbstraction.CircleImage), typeof(ImageCircleRenderer))]

namespace FormulaOneApp.WinPhone.Controls
{
    /// <summary>
    /// ImageCircle Implementation
    /// </summary>
    public class ImageCircleRenderer : ImageRenderer
    {
        /// <summary>
        /// Used for registration with dependency service
        /// </summary>
        public static void Init()
        {
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        protected override void OnElementPropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
        {
            base.OnElementPropertyChanged(sender, e);
            if (Control != null && Control.Clip == null)
            {
                var min = Math.Min(Element.Width, Element.Height) / 2.0f;
                if (min <= 0)
                    return;
                Control.Clip = new EllipseGeometry
                {
                    Center = new System.Windows.Point(min, min),
                    RadiusX = min,
                    RadiusY = min
                };
            }
        }
    }
}