如何在图上写字，或者画画。

本来是应该用InkCanvas，但是InkCanvas在生成新图片的时候会不带背景。

所以可以用Canvas，自己在.cs代码里写轨迹。

这个例子是，图上用textblock添加文字，或者是在canvas中手动绘制图形。

xaml:

  <Grid>        <StackPanel Orientation="Vertical">            <TextBlock Text="Add your text here:" FontSize="20" Margin="0,20,0,0"/>            <TextBox x:Name="textbox" Margin="0,20,0,0"/>            <Canvas x:Name="inkCanvas">                <Grid x:Name="newimg" Width="400" >                    <Image Source="Assets/1.png" x:Name="image" Margin="0,100,0,0" />                    <TextBlock FontSize="40" x:Name="textblock" TextWrapping="Wrap"                           VerticalAlignment="Center" HorizontalAlignment="Center" Foreground="Black"/>                </Grid>            </Canvas>            <StackPanel Orientation="Horizontal">                <Button Content="Add text to image"  Margin="10,20,0,0" Click="Button_Click"/>                <Button Content="Draw on the image" HorizontalAlignment="Center" Margin="10,20,0,0" Click="Button_Click_1" />            </StackPanel>        </StackPanel>        <StackPanel VerticalAlignment="Bottom">            <Image x:Name="newimage"/>        </StackPanel>    </Grid>

.cs

        public MainPage()        {            this.InitializeComponent();            this.NavigationCacheMode = NavigationCacheMode.Required;            inkCanvas.PointerPressed += inkCanvas_PointerPressed;            inkCanvas.PointerMoved += inkCanvas_PointerMoved;            inkCanvas.PointerReleased += inkCanvas_PointerReleased;            inkCanvas.PointerExited += inkCanvas_PointerReleased;        }        /// <summary>        /// Invoked when this page is about to be displayed in a Frame.        /// </summary>        /// <param name="e">Event data that describes how this page was reached.        /// This parameter is typically used to configure the page.</param>        protected override void OnNavigatedTo(NavigationEventArgs e)        {            // TODO: Prepare page for display here.            // TODO: If your application contains multiple pages, ensure that you are            // handling the hardware Back button by registering for the            // Windows.Phone.UI.Input.HardwareButtons.BackPressed event.            // If you are using the NavigationHelper provided by some templates,            // this event is handled for you.        }        private async void Button_Click(object sender, RoutedEventArgs e)        {            string text = textbox.Text.ToString();            textblock.Text = text;            RenderTargetBitmap renderbmp = new RenderTargetBitmap();            await renderbmp.RenderAsync(newimg);            newimage.Source = renderbmp;        }        private async void Button_Click_1(object sender, RoutedEventArgs e)        {            RenderTargetBitmap renderbmp = new RenderTargetBitmap();            await renderbmp.RenderAsync(inkCanvas);            newimage.Source = renderbmp;        }        Windows.UI.Xaml.Shapes.Path _Current;        private void inkCanvas_PointerReleased(object sender, PointerRoutedEventArgs e)        {            _Current = null;        }        private void inkCanvas_PointerMoved(object sender, PointerRoutedEventArgs e)        {            var pointer = e.GetCurrentPoint(inkCanvas);            if (!pointer.Properties.IsLeftButtonPressed || _Current == null)                return;            var segments = (_Current.Data as PathGeometry).Figures.First().Segments.First() as PolyLineSegment;            segments.Points.Add(pointer.Position);        }        private void inkCanvas_PointerPressed(object sender, PointerRoutedEventArgs e)        {            var pointer = e.GetCurrentPoint(inkCanvas);            if (!pointer.Properties.IsLeftButtonPressed)                return;            _Current = new Windows.UI.Xaml.Shapes.Path            {                Data = new PathGeometry                {                    Figures = {new PathFigure { StartPoint = pointer.Position,Segments = { new PolyLineSegment() } } }                },  Stroke = new SolidColorBrush(Colors.Black),                StrokeThickness = 4d,            };            inkCanvas.Children.Add(_Current);        }