iPhone Core Graphics thicker dashed line for subview

Question

I have a UIView and within it I've drawn a line using Core Graphics by overriding drawRect. This view also contains one subview which also draws a line. However, whilst both views are using pretty much the same code (for testing purposes at least), the lines drawn on them do not appear the same:

As you can see - the dashed line at the top is noticeably thicker than the bottom one and I have no idea why. Below is the code used by the two UIViews in their drawRect methods. If you have any idea why this is happening then I'd appreciate your help and advice!

First View:

CGContextRef context = UIGraphicsGetCurrentContext();

CGContextSetStrokeColorWithColor(context, [[UIColor whiteColor] CGColor]);

CGFloat dashes[] = {1,1};

CGContextSetLineDash(context, 0.0, dashes, 2);
CGContextSetLineWidth(context, 0.6);

CGContextMoveToPoint(context, CGRectGetMinX(rect), CGRectGetMaxY(rect));
CGContextAddLineToPoint(context, CGRectGetMaxX(rect), CGRectGetMaxY(rect));

CGContextStrokePath(context);

SubUIView *view = [[SubUIView alloc] initWithFrame:rect];
[self addSubview:view];
[view release];

The view is definitely only being drawn once. I appreciate drawRect may not be the best place for adding a subview but the problem remains even with it added in the main initWithFrame method.

Second View:

CGContextRef context = UIGraphicsGetCurrentContext();

CGContextSetStrokeColorWithColor(context, [[UIColor whiteColor] CGColor]);

CGFloat dashes[] = {1,1};

CGContextSetLineDash(context, 0.0, dashes, 2);
CGContextSetLineWidth(context, 0.6);

CGContextMoveToPoint(context, CGRectGetMinX(rect), CGRectGetMidY(rect));
CGContextAddLineToPoint(context, CGRectGetMaxX(rect), CGRectGetMidY(rect));

CGContextStrokePath(context);

Answer 1

It could be a result of anti-aliasing if your rect does not fall on integers. You can disable anti-aliasing with CGContextSetShouldAntialias( context, NO ). I think there's also a function for making a rect integral, but I can't remember what it is.