AddHorizontalSpan: off by 1px on frameless plots #2051
Description
There's a 1px white upper border when using horizontal axis spans
I suspect this is typically covered-up when plots have black spines around the frame
ScottPlot.Plot plt = new(pbGraph.Width, pbGraph.Height);
plt.Frameless();
plt.AddSignal(ratioImage.GreenData.AverageByColumn(), 1, Color.Green);
plt.AddSignal(ratioImage.RedData.AverageByColumn(), 1, Color.Red);
plt.AddHorizontalSpan(structure.Min, structure.Max, Color.FromArgb(20, Color.Blue));
pbGraph.Image = plt.GetBitmap();