Dotted Line for PDF Rendering in iOS

tags ios line draw cgcontext dotted-line

I wont to know how to render a dotted line on a pdf.

CGContextRef currentContext = UIGraphicsGetCurrentContext();

CGContextSetStrokeColorWithColor(currentContext, [UIColor grayColor].CGColor);
CGFloat lengths[] = {0, 8};
CGContextSetLineCap(currentContext, kCGLineCapRound);
CGContextSetLineWidth(currentContext, 1);
CGContextSetLineDash(currentContext, 0.0f, lengths, 2);

CGContextBeginPath(currentContext);
CGContextMoveToPoint(currentContext, x1, y1);
CGContextAddLineToPoint(currentContext, x2, y2);

CGContextClosePath(currentContext);
CGContextDrawPath(currentContext, kCGPathStroke);

From what I understand, this code should produce a dotted line that has 0 units of painted (dot) followed by 8 units of unpainted line. It does not. It produces the following instead:

A dot followed by 8 units of empty space followed by a dot followed by 1 unit of empty space followed by a dot followed by 8 units of empty space...etc. I would post the picture but I don't have enough rep points.

What am I doing wrong?