UIView drawRect: is it possible to stroke inside a path?

问题

With core graphics, is it possible to stroke the inside of a path? As opposed to the line weight being drawn half on the outside and half on the inside of a stroked path?

The reason being it would be easier to control the visible thickness of the stroke if say part of a view is on the screen edge and part is not. The part on the screen edge gets cut off, while the view edge that is fully on screen looks thicker (as both sides if the stroke are visible).

回答1:

Clip to the path before you stroke it.

回答2:

This draws no stroke:

- (void)drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetStrokeColorWithColor(context, [UIColor darkGrayColor].CGColor);
    CGContextSetLineWidth(context, 14);
    CGRect rrect = CGRectMake(CGRectGetMinX(rect), CGRectGetMinY(rect), CGRectGetWidth(rect), CGRectGetHeight(rect));
    CGFloat radius = 30;
    CGFloat minx = CGRectGetMinX(rrect), midx = CGRectGetMidX(rrect), maxx = CGRectGetMaxX(rrect);
    CGFloat miny = CGRectGetMinY(rrect), midy = CGRectGetMidY(rrect), maxy = CGRectGetMaxY(rrect);
    CGContextMoveToPoint(context, minx, midy);
    CGContextAddArcToPoint(context, minx, miny, midx, miny, radius);
    CGContextAddArcToPoint(context, maxx, miny, maxx, midy, radius);
    CGContextAddArcToPoint(context, maxx, maxy, midx, maxy, radius);
    CGContextAddArcToPoint(context, minx, maxy, minx, midy, radius);
    CGContextClosePath(context);
    CGContextClip(context);
    CGContextDrawPath(context, kCGPathStroke);
}

EDIT: This is what worked (according to the correct answer):

- (void)drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetStrokeColorWithColor(context, [UIColor darkGrayColor].CGColor);
    CGContextSetFillColorWithColor(context, [UIColor blackColor].CGColor);
    CGContextSetLineWidth(context, 14);
    CGRect pathRect = CGRectMake(10, 10, rect.size.width -20, rect.size.height -20);
    CGPathRef path = [UIBezierPath bezierPathWithRoundedRect:pathRect cornerRadius:20].CGPath;
    CGContextAddPath(context, path);
    CGContextClip(context);
    CGContextAddPath(context, path);
    CGContextDrawPath(context, kCGPathEOFillStroke);

}

来源：https://stackoverflow.com/questions/14258924/uiview-drawrect-is-it-possible-to-stroke-inside-a-path

标签

uiview

core-graphics

stroke