public Rectangle GetAutoSizePixels()
{
// uses full map, but if it's too close to localsize reverts to local
var full = GetFullMapSizePixels();
var local = GetLocalSizePixels();
const double delta = 0.15;
if (Math.Abs(full.Left - local.Left) / (double)full.Width < delta
&& Math.Abs(full.Width - local.Width) / (double)full.Width < delta
&& Math.Abs(full.Top - local.Top) / (double)full.Height < delta
&& Math.Abs(full.Bottom - local.Bottom) / (double)full.Height < delta)
return local;
else return full;
}