How to draw a rounded rectangle in Core Graphics / Quartz 2D?

Question

I need to draw an outline for a rounded rectangle. I know I can make lines and arcs, but maybe there is also a function for rounded rects?

Answer 1

I don't think there is a nice predefined way to do this. However, this question has the code necessary to do it using line segments:

http://stackoverflow.com/questions/1031930/how-is-a-rounded-rect-view-with-transparency-done-on-iphone/1031936#1031936

Answer 2

There is no prepackaged way to this, you must combine arcs in order to do this, apples quartzdemo project shows the code to do this, here is a reference Quartz Demo and here is the code they provide

  // As a bonus, we'll combine arcs to create a round rectangle! 

// Drawing with a white stroke color 
 CGContextRef context=UIGraphicsGetCurrentContext()
CGContextSetRGBStrokeColor(context, 1.0, 1.0, 1.0, 1.0); 

// If you were making this as a routine, you would probably accept a rectangle 
// that defines its bounds, and a radius reflecting the "rounded-ness" of the rectangle. 
CGRect rrect = CGRectMake(210.0, 90.0, 60.0, 60.0); 
CGFloat radius = 10.0; 
// NOTE: At this point you may want to verify that your radius is no more than half 
// the width and height of your rectangle, as this technique degenerates for those cases. 

// In order to draw a rounded rectangle, we will take advantage of the fact that 
// CGContextAddArcToPoint will draw straight lines past the start and end of the arc 
// in order to create the path from the current position and the destination position. 

// In order to create the 4 arcs correctly, we need to know the min, mid and max positions 
// on the x and y lengths of the given rectangle. 
CGFloat minx = CGRectGetMinX(rrect), midx = CGRectGetMidX(rrect), maxx = CGRectGetMaxX(rrect); 
CGFloat miny = CGRectGetMinY(rrect), midy = CGRectGetMidY(rrect), maxy = CGRectGetMaxY(rrect); 

// Next, we will go around the rectangle in the order given by the figure below. 
//       minx    midx    maxx 
// miny    2       3       4 
// midy   1 9              5 
// maxy    8       7       6 
// Which gives us a coincident start and end point, which is incidental to this technique, but still doesn't 
// form a closed path, so we still need to close the path to connect the ends correctly. 
// Thus we start by moving to point 1, then adding arcs through each pair of points that follows. 
// You could use a similar tecgnique to create any shape with rounded corners. 

// Start at 1 
CGContextMoveToPoint(context, minx, midy); 
// Add an arc through 2 to 3 
CGContextAddArcToPoint(context, minx, miny, midx, miny, radius); 
// Add an arc through 4 to 5 
CGContextAddArcToPoint(context, maxx, miny, maxx, midy, radius); 
// Add an arc through 6 to 7 
CGContextAddArcToPoint(context, maxx, maxy, midx, maxy, radius); 
// Add an arc through 8 to 9 
CGContextAddArcToPoint(context, minx, maxy, minx, midy, radius); 
// Close the path 
CGContextClosePath(context); 
// Fill & stroke the path 
CGContextDrawPath(context, kCGPathFillStroke); 

Answer 3

If you want To have rounded corners on any UIView (or subclass) the easy way is to set the cornerRadius property on the view's layer. See http://stackoverflow.com/questions/2448725/preview-rounded-image-in-iphone/2448903#2448903