IOS: create a UIImage or UIImageView with rounded corners

Is it possible create an UIImage or an UIImageView with rounded corners? Because I want take an UIImage and show it inside an UIImageView, but I don't know how to do it.

Yes, it is possible.
Import the QuartzCore (#import <QuartzCore/QuartzCore.h>) header and play with the layer property of the UIImageView.

yourImageView.layer.cornerRadius = yourRadius;
yourImageView.clipsToBounds = YES;

See the CALayer class reference for more info.

Try this Code For Round Image Import QuartzCore framework simple way to create Round Image

imageView.layer.backgroundColor=[[UIColor clearColor] CGColor];
imageView.layer.cornerRadius=20;
imageView.layer.borderWidth=2.0;
imageView.layer.masksToBounds = YES;
imageView.layer.borderColor=[[UIColor redColor] CGColor];

Objective-C

-(UIImage *)makeRoundedImage:(UIImage *) image 
                      radius: (float) radius;
{
  CALayer *imageLayer = [CALayer layer];
  imageLayer.frame = CGRectMake(0, 0, image.size.width, image.size.height);
  imageLayer.contents = (id) image.CGImage;

  imageLayer.masksToBounds = YES;
  imageLayer.cornerRadius = radius;
  
  UIGraphicsBeginImageContext(image.size);
  [imageLayer renderInContext:UIGraphicsGetCurrentContext()];
  UIImage *roundedImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  
  return roundedImage;
}

Swift 3

func makeRoundedImage(image: UIImage, radius: Float) -> UIImage {
    var imageLayer = CALayer()
    imageLayer.frame = CGRect(x: 0, y: 0, width: image.size.width, height: image.size.height)
    imageLayer.contents = image.cgImage
    
    imageLayer.masksToBounds = true
    imageLayer.cornerRadius = radius
    
    UIGraphicsBeginImageContext(image.size)
    imageLayer.render(in: UIGraphicsGetCurrentContext())
    var roundedImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    
    return roundedImage
}

uiimageview.layer.cornerRadius = uiimageview.frame.size.height/2;
uiimageview.clipToBounds = YES;

#import <QuartzCore/QuartzCore.h>

// UIImageView+OSExt.h
#import <UIKit/UIKit.h>

@interface UIImageView (OSExt)
- (void)setBorder:(CGFloat)borderWidth color:(UIColor*)color;
@end

// UIImageView+OSExt.m
#import "UIImageView+OSExt.h"

@implementation UIImageView (OSExt)
- (void)layoutSublayersOfLayer:(CALayer *)layer
{
    for ( CALayer *sub in layer.sublayers )
    {
        if ( YES == [sub.name isEqual:@"border-shape"])
        {
            CGFloat borderHalf = floor([(CAShapeLayer*)sub lineWidth] * .5);
            sub.frame = layer.bounds;
            [sub setBounds:CGRectInset(layer.bounds, borderHalf, borderHalf)];
            [sub setPosition:CGPointMake(CGRectGetMidX(layer.bounds),
                                       CGRectGetMidY(layer.bounds))];
        }
    }
}

- (void)setBorder:(CGFloat)borderWidth color:(UIColor*)color
{
    assert(self.frame.size.width == self.frame.size.height);
    for ( CALayer *sub in [NSArray arrayWithArray:self.layer.sublayers] )
    {
        if ( YES == [sub.name isEqual:@"border-shape"])
        {
            [sub removeFromSuperlayer];
            break;
        }
    }
    
    CGFloat borderHalf = floor(borderWidth * .5);
    self.layer.cornerRadius = self.layer.bounds.size.width * .5;

    CAShapeLayer *circleLayer = [CAShapeLayer layer];
    self.layer.delegate = (id<CALayerDelegate>)self;
    circleLayer.name = @"border-shape";
    [circleLayer setBounds:CGRectInset(self.bounds, borderHalf, borderHalf)];
    [circleLayer setPosition:CGPointMake(CGRectGetMidX(self.layer.bounds),
                                         CGRectGetMidY(self.layer.bounds))];
    [circleLayer setPath:[[UIBezierPath bezierPathWithOvalInRect:circleLayer.bounds] CGPath]];
    [circleLayer setStrokeColor:color.CGColor];
    [circleLayer setFillColor:[UIColor clearColor].CGColor];
    [circleLayer setLineWidth:borderWidth];

    {
    circleLayer.shadowOffset = CGSizeZero;
    circleLayer.shadowColor = [[UIColor whiteColor] CGColor];
    circleLayer.shadowRadius = borderWidth;
    circleLayer.shadowOpacity = .9f;
    circleLayer.shadowOffset = CGSizeZero;
    }

    // Add the sublayer to the image view's layer tree
    [self.layer addSublayer:circleLayer];

    // old variant
    //CALayer *layer = self.layer;
    //layer.masksToBounds = YES;
    //layer.cornerRadius = self.frame.size.width * 0.5;
    //layer.borderWidth = borderWidth;
    //layer.borderColor = color;
}
@end

Setting cornerRadius and clipsToBounds is the right way to do this. However if the view's size changes, the radius will not update. In order to get proper resizing and animation behavior, you need to create a UIImageView subclass.

class RoundImageView: UIImageView {
    override var bounds: CGRect {
        get {
            return super.bounds
        }
        set {
            super.bounds = newValue
            setNeedsLayout()
        }
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        layer.cornerRadius = bounds.width / 2.0
        clipsToBounds = true
    }
}

Try this to get rounded corners of the image View and also to colour the corners:

imageView.layer.cornerRadius = imageView.frame.size.height/2;
imageView.layer.masksToBounds = YES;
imageView.layer.borderColor = [UIColor colorWithRed:148/255. green:79/255. blue:216/255. alpha:1.0].CGColor;
imageView.layer.borderWidth=2;

Condition*: The height and the width of the imageView must be same to get rounded corners.

1. layer.cornerRadius = imageviewHeight/2

2. layer.masksToBounds = true

It is possible but I'll advice you to create transparent png image (mask) with round corners and place it over you image with UIImageView. It might be quicker solution (for example if you need animations or scrolling).

Here how i set my rounded avatar at the center of it contain view:

-(void)setRoundedAvatar:(UIImageView *)avatarView toDiameter:(float)newSize atView:(UIView *)containedView;
{
    avatarView.layer.cornerRadius = newSize/2;
    avatarView.clipsToBounds = YES;

    avatarView.frame = CGRectMake(0, 0, newSize, newSize);
    CGPoint centerValue = CGPointMake(containView.frame.size.width/2, containedView.frame.size.height/2);
    avatarView.center = centerValue;
}

> Circle with UIBeizerPath #Swift-3 && #imageExtension

class ViewController: UIViewController {
    @IBOutlet weak var imageOutlet: UIImageView!
    override func viewDidLoad() {
        super.viewDidLoad()
        let image = UIImage(named: "IMG_0001.JPG")
        if let image = image {
            let renderimage = image.imageCroppingBezierPath(path: UIBezierPath(arcCenter: CGPoint(x:image.size.width/2,y:image.size.width/2 )  , radius: 200, startAngle: 0, endAngle:  (2 * CGFloat(M_PI) ), clockwise: true) )
                imageOutlet.image = renderimage
        }
    }
}


extension UIImage {
    func imageCroppingBezierPath(path:UIBezierPath) ->UIImage {

        let frame = CGRect(x: 0, y: 0, width: self.size.width, height: self.size.height)

        //Defining a graphic context  to paint on
        UIGraphicsBeginImageContextWithOptions(self.size, false, 0.0)
        //Get the current graphics context (if it exists)
        let context = UIGraphicsGetCurrentContext()
        //save the current graphic context
        context?.saveGState()
        // clipping area
        path.addClip()
        self.draw(in: frame)

        //To extract an image from our canvas
        let image = UIGraphicsGetImageFromCurrentImageContext()
        //restore graphic context
        context?.restoreGState()
        //remove current context from stack
        UIGraphicsEndImageContext()
        return image!
    }
}

# import QuartzCore framework
imageView.layer.cornerRadius=imgvwUser.frame.size.width/2;
imageView.layer.masksToBounds = YES;

The height and the width of the imageView must be same to get rounded corners.