wpf如何使框架元素将图形视觉存储为位图并在渲染时显示？

Question

I want to make my framework element, signalgraph, display the signal (a DrawingVisual) as a bitmap and then render the bitmap when WPF goes through a rendering pass. I'm guessing I override onRender for the FrameworkElement, but I'm not sure. I just want to try converting everything to a bitmap because I think the program renders slow because there are too many lines, and saving it to a bit map would hopefully improve performance.

As a test, I tried to add a SkyBlue Rectangle to the framework element, but it is not displaying.

I create a rectangle that inherits from Shape, which inherits from Visual. I then use the RenderTargetBitmap class to render the visual, and then set the output render of the rendertargetbitmap as the source of an Image. Image is a framework element, so I then just add it to the visual collection in the hopes that it will display, but nothing appears.

    Rectangle myRect = new Rectangle();
    myRect.Stroke = System.Windows.Media.Brushes.Black;
    myRect.Fill = System.Windows.Media.Brushes.SkyBlue;
    myRect.HorizontalAlignment = HorizontalAlignment.Left;
    myRect.VerticalAlignment = VerticalAlignment.Center;
    myRect.Height = 200;
    myRect.Width = 200;
    BitmapImage = new RenderTargetBitmap(1000, 1000, 96, 96, PixelFormats.Default);
    BitmapImage.Render(myRect);
    GraphImage = new Image();
    GraphImage.Source = BitmapImage;
    visuals.Add(GraphImage); //visuals is a VisualCollection

Not sure what I'm doing wrong, but any ideas or alternatives that I might try to save the lines drawn on the canvas to a bit map would be appreciated.

Answer 1

If performance is major factor, I would suggest you instead of going with WPF shapes, try DrawingVisual whose performance is very good compare to WPF shapes.

It's very easy to use and integrate to project. Simply you need to create one VisulHost say Canvas which will hold VisualCollection of all drawing visual , you want to draw. Override few these two FrameworkElement members - GetVisualChild and VisualChildrenCount .

You can read more about here on MSDN - Using DrawingVisual Objects .

Also can refer to this for already available working solution - WPF DrawTools .