Draft full screen image viewer

ImageViewer.cs

public class ImageViewer : NControlView
    {
        private Image _image;
        private NGraphics.Point _startPoint;

        public ImageViewer()
        {
            IsClippedToBounds = true;

            _image = new Image();
            _image.InputTransparent = true;

            Content = _image;
        }

        public static BindableProperty SourceProperty =
            BindableProperty.Create(nameof(Source),
                                    typeof(ImageSource),
                                    typeof(ImageViewer),
                                    default(ImageSource),
                                    BindingMode.TwoWay,
                                    propertyChanged: (bindable, oldValue, newValue) =>
                {
                    var ctrl = (ImageViewer)bindable;
                    ctrl.Source = (ImageSource)newValue;
                });

        public event Action<object, NGraphics.Point> OnTapped;

        private bool _isMoved;

        public ImageSource Source
        {
            get { return (ImageSource)GetValue(SourceProperty); }
            set
            {
                SetValue(SourceProperty, value);
                _image.Source = value;
            }
        }

        public override bool TouchesBegan(System.Collections.Generic.IEnumerable<NGraphics.Point> points)
        {
            base.TouchesBegan(points);
            _startPoint = points.FirstOrDefault();
            _startPoint.X -= _image.TranslationX;
            _startPoint.Y -= _image.TranslationY;
            _isMoved = false;

            return true;
        }

        public override bool TouchesMoved(System.Collections.Generic.IEnumerable<NGraphics.Point> points)
        {
            base.TouchesMoved(points);
            var newPoint = points.FirstOrDefault();
            var diff = new NGraphics.Point(newPoint.X - _startPoint.X, newPoint.Y - _startPoint.Y);

            _isMoved = _isMoved
                || (_image.TranslationX != diff.X
                    && _image.TranslationY != diff.Y);

            _image.TranslationX = diff.X;
            _image.TranslationY = diff.Y;

            return true;
        }

        public override bool TouchesEnded(System.Collections.Generic.IEnumerable<NGraphics.Point> points)
        {
            base.TouchesEnded(points);
            if (!_isMoved)
            {
                OnTapped?.Invoke(this, points.First());
            }
            _isMoved = false;
            return true;
        }

    }