How to get a 1 pixel line with NSBezierPath?

Question

I'm developing a custom control. One of the requirements is to draw lines. Although this works, I noticed that my 1 pixel wide lines do not really look like 1 pixel wide lines - I know, they're not really pixels but you know what I mean. They look more like two or three pixels wide. This becomes very apparent when I draw a dashed line with a 1 pixel dash and a 2 pixel gap. The 1 pixel dashes actually look like tiny lines in stead of dots.

I've read the Cocoa Drawing documentation and although Apple mentions the setLineWidth method, changing the line width to values smaller than 1.0 will only make the line look more vague and not thinner.

So, I suspect there's something else influencing the way my lines look.

Any ideas?

Answer 1

Bezier paths are drawn centered on their path, so if you draw a 1 pixel wide path along the X-coordinate, the line actually draws along Y-coordinates { -0.5, 0.5 } The solution is usually to offset the coordinate by 0.5 so that the line is not drawn in the sub pixel boundaries. You should be able to shift your bounding box by 0.5 to get sharper drawing behavior.