Anti Aliasing on Screen Percentage

I have used Screen Percentage for better rendering quality.

I have used r.ScreenPercentage Command for it.

I have used r.ScreenPercentage 200. I got bellow result.

After I have used r.ScreenPercentage 300. I got bellow result.

I am getting Anti Aliasing in Straight Lines.

Is there any solution for this?
Is there any way take screenshot with better quality?