Control.cs

using System;
using System.IO;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Media.Imaging;
using SkiaSharp;

namespace Microcharts.Uwp
{
    [TemplatePart(Name = ImagePart, Type = typeof(Image))]
    public partial class SecondChartView: Control
    {
        public const string ImagePart = "PART_Image";

        public SecondChartView()
        {
            this.DefaultStyleKey =  typeof(SecondChartView);

            SizeChanged          += OnSizeChanged;
        }

        #region Properties

        #region Chart property

        public static readonly DependencyProperty ChartProperty = DependencyProperty.Register(nameof(Chart),
                                                                                              typeof(Chart),
                                                                                              typeof(SecondChartView),
                                                                                              new PropertyMetadata(null, ChartPropertyChanged));

        public Chart Chart
        {
            get => GetValue(ChartProperty) as Chart;
            set => SetValue(ChartProperty, value);
        }

        private static void ChartPropertyChanged(object sender, DependencyPropertyChangedEventArgs eventArgs)
        {
            ((SecondChartView)sender).ChartPropertyChanged();
        }

        private void ChartPropertyChanged()
        {
            GenerateSource();
        }

        #endregion Chart property

        public static readonly DependencyProperty ImageSourceProperty = DependencyProperty.Register(nameof(ImageSource),
                                                                                                    typeof(ImageSource),
                                                                                                    typeof(SecondChartView),
                                                                                                    new PropertyMetadata(null));

        public ImageSource ImageSource
        {
            get => GetValue(ImageSourceProperty) as ImageSource;
            private set => SetValue(ImageSourceProperty, value);
        }

        #endregion Properties

        private void GenerateSource()
        {
            if (Chart == null)
            {
                ImageSource = null;
                return;
            }

            var actualWidth  = (int)ActualWidth;
            var actualHeight = (int)ActualHeight;

            if (actualHeight <= 0
             || actualWidth  <= 0)
            {
                ImageSource = null;
                Console.WriteLine("SKipped, no size");
                return;
            }
            Console.WriteLine("Generated {0}/{1}", actualWidth, actualHeight);

            ApplyTemplate();

            // apply render tweaks:
            Chart.IsAnimated = false;
            // end apply render tweaks

            MemoryStream ms;
            using (var bitmap = new SKBitmap(actualWidth, actualHeight))
            {
                using (var canvas = new SKCanvas(bitmap))
                {
                    Chart.Draw(canvas, actualWidth, actualHeight);
                    canvas.Flush();
                }

                ms = new MemoryStream();
                bitmap.Encode(ms, SKEncodedImageFormat.Png, 100);
            }
            ms.Position = 0;
            var result = new BitmapImage();
            result.SetSource(ms.AsRandomAccessStream());

            _partImage.Source = result;
            Console.WriteLine("Source set");
        }

        private Image _partImage;

        protected override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            _partImage = (Image)GetTemplateChild(ImagePart);
        }

        private void OnSizeChanged(object sender, SizeChangedEventArgs args)
        {
            GenerateSource();
        }
    }
}

TemplateSnippet.xaml

            <Style TargetType="uwp1:SecondChartView">
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate>
                            <Image x:Name="PART_Image" />
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>