Getting a DrawingContext for a wpf WriteableBitmap

Question

Is there a way to get a DrawingContext (or something similar) for a WriteableBitmap? I.e. something to allow you to call simple DrawLine

Answer 1

A different way to solve this problem is to use a RenderTargetBitmap as a backing store, just like in the WriteableBitmap example. Then you can create and issue WPF drawing commands to it whenever you want. For example:

// create the backing store in a constructor
var backingStore = 
      new RenderTargetBitmap(200,200,97,97,PixelFormats.Pbgra32);
myImage.Source = backingStore;

// whenever you want to update the bitmap, do:
var drawingVisual = new DrawingVisual();
var drawingContext = drawingVisual.RenderOpen();
{
    // your drawing commands go here
    drawingContext.DrawRectangle(
            Brushes.Red, new Pen(),
            new Rect(this.RenderSize));
}
Render(drawingContext);
drawingContext.Close();
backingStore.Render(drawingVisual);

If you want to redraw this RenderTargetBitmap every frame, you can catch the CompositionTarget.Rendering event, like this:

CompositionTarget.Rendering += MyRenderingHandler;