WPF DrawingVisual绘图DEMO

在winform 中我们使用GDI+ 进行绘图，到了WPF， 使用的是DirectX渲染，所以不能使用GDI+ 进行绘图，

但是其实WPF中也是有绘图单元的，本文用DrawingVisual 来进行基础的绘图，在一张图片上进行画正弦信号图：

先从Image类继承一个绘图的单元：
public class DrawingImage:Image
    {
        private List<Visual> visuals = new List<Visual>();

        protected override Visual GetVisualChild(int index)
        {
            return visuals[index];
        }
        protected override int VisualChildrenCount
        {
            get
            {
                return visuals.Count;
            }
        }

        public void AddVisual(Visual visual)
        {
            visuals.Add(visual);

            base.AddVisualChild(visual);
            base.AddLogicalChild(visual);
        }

        public void DeleteVisual(Visual visual)
        {
            visuals.Remove(visual);

            base.RemoveVisualChild(visual);
            base.RemoveLogicalChild(visual);
        }

        public DrawingVisual GetVisual(Point point)
        {
            HitTestResult hitResult = VisualTreeHelper.HitTest(this, point);
            return hitResult.VisualHit as DrawingVisual;
        }

        private List<DrawingVisual> hits = new List<DrawingVisual>();
        public List<DrawingVisual> GetVisuals(Geometry region)
        {
            hits.Clear();
            GeometryHitTestParameters parameters = new GeometryHitTestParameters(region);
            HitTestResultCallback callback = new HitTestResultCallback(this.HitTestCallback);
            VisualTreeHelper.HitTest(this, null, callback, parameters);
            return hits;
        }

        private HitTestResultBehavior HitTestCallback(HitTestResult result)
        {
            GeometryHitTestResult geometryResult = (GeometryHitTestResult)result;
            DrawingVisual visual = result.VisualHit as DrawingVisual;
            if (visual != null &&
                geometryResult.IntersectionDetail == IntersectionDetail.FullyInside)
            {
                hits.Add(visual);
            }
            return HitTestResultBehavior.Continue;
        }
    }

XAML页面中使用
<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApplication1"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Grid x:Name="Main">
        <local:DrawingImage x:Name="panel" Source="Tulips.png" Stretch="Fill"></local:DrawingImage>
               
    </Grid>
</Window>

后台添加绘图程序：
public MainWindow()
        {
            InitializeComponent();
            DrawingVisual visualx = new DrawingVisual();
            using (DrawingContext dc = visualx.RenderOpen())
            {
                dc.PushOpacity(0.8);
                dc.PushOpacityMask(Brushes.Red);
                Pen pen = new Pen(Brushes.Green, 2);
                for (int i = 0; i < 500; i ++)
                {                
                    dc.DrawLine(pen, new Point(i*2, Math.Sin(i*0.1)*100 + 200), new Point((i + 1)*2, Math.Sin((i + 1)*0.1)*100 + 200));
                    dc.DrawText(new FormattedText("Hello, World!", CultureInfo.CurrentCulture, FlowDirection.LeftToRight, new Typeface("Arial"), 10, Brushes.CornflowerBlue), new Point(i * 2, Math.Sin(i * 0.1) * 100 + 200));
                }                
            }
            panel.AddVisual(visualx);         
        }

看下效果：