How to get pixel perfect drawing with cocoa

Question

I'm trying to draw some of my UI elements in Cocoa, mainly icons for buttons, but I'm having great difficulty getting the kind of precision I'd like.

I'm using super simple code like this to draw rectangles:

[[NSColor redColor] set];
[NSBezierPath strokeRect:myRect];

But what I'm seeing is the red rectangle line is always faded.

What am I missing here?