Question

Hopefully this’ll be a fairly simple answer, but it’s not the easiest thing to google for.

I’m planning to do a lot of painting using simple shapes, but the actual result doesn’t need to be displayed to the user until the final stage, so for the sake of speed, I was wondering if there were existing methods in c#/WPF to draw simple shapes to a buffer without the overhead of a BitmapSource, so at the end I can just copy it into a WritableBitmap.

Something like

PixelFormat pixelFormat = PixelFormats.Default;
int stride = bitmapWidth * pixelFormat.BitsPerPixel / 8;
byte[] pixels new byte[bitmapHeight * stride];
*some static library*.DrawOval(xpos=10,ypos=10,radius=5, pixels, stride, pixelFormat);

Thanks

Answer 1

“Drawing shapes to a buffer” in WPF could be done by drawing shapes into a DrawingVisual using a DrawingContext. When drawing is finished, the DrawingVisual can be rendered into a RenderTargetBitmap.

Example:

DrawingVisual drawingVisual = new DrawingVisual();

using (DrawingContext drawingContext = drawingVisual.RenderOpen())
{
    drawingContext.DrawEllipse(null, new Pen(Brushes.Black, 1), new Point(100, 100), 50, 50);
}

Drawing drawing = drawingVisual.Drawing;

using (DrawingContext drawingContext = drawingVisual.RenderOpen())
{
    drawingContext.DrawDrawing(drawing);
    drawingContext.DrawEllipse(null, new Pen(Brushes.Black, 1), new Point(100, 100), 60, 60);
}

RenderTargetBitmap bitmap = new RenderTargetBitmap(200, 200, 96, 96, PixelFormats.Default);
bitmap.Render(drawingVisual);