Наверное, вот ответ на мой вопрос :)
_plotBitmap.Lock();
var b = new Bitmap(_plotBitmap.PixelWidth,
_plotBitmap.PixelHeight,
_plotBitmap.BackBufferStride,
System.Drawing.Imaging.PixelFormat.Format24bppRgb,
_plotBitmap.BackBuffer);
using(var bitmapGraphics = System.Drawing.Graphics.FromImage(b))
{
bitmapGraphics.SmoothingMode = SmoothingMode.HighSpeed;
bitmapGraphics.InterpolationMode = InterpolationMode.NearestNeighbor;
bitmapGraphics.CompositingMode = CompositingMode.SourceCopy;
bitmapGraphics.CompositingQuality = CompositingQuality.HighSpeed;
bitmapGraphics.DrawLine(Pens.Gold,2,2,222,222);
}
_plotBitmap.AddDirtyRect(new Int32Rect(0,0,_plotBitmap.PixelWidth,_plotBitmap.PixelHeight));
_plotBitmap.Unlock();