Add rounded corners to all UIImageViews

Question

I would like to add some rounded corners to all of the UIImageViews in my project. I have already got the code working, but am having to apply it to every image; should I subclass UIImageView to add this? If so, can someone give me some pointers as to how to do this?

Here is the code

- (void)viewDidLoad {
    [super viewDidLoad];
    NSString *mainpath = [[NSBundle mainBundle] bundlePath];
    welcomeImageView.image = [UIImage imageWithContentsOfFile:[mainpath stringByAppendingString:@"/test.png"]];
    welcomeImageView.layer.cornerRadius = 9.0;
    welcomeImageView.layer.masksToBounds = YES;
    welcomeImageView.layer.borderColor = [UIColor blackColor].CGColor;
    welcomeImageView.layer.borderWidth = 3.0;
    CGRect frame = welcomeImageView.frame;
    frame.size.width = 100;
    frame.size.height = 100;
    welcomeImageView.frame = frame;
}

Answer 1

Check this - Rounded Corners on UIImage

The layer modification seems to be the best way.

UIImageView * roundedView = [[UIImageView alloc] initWithImage: [UIImage imageNamed:@"wood.jpg"]];
// Get the Layer of any view
CALayer * l = [roundedView layer];
[l setMasksToBounds:YES];
[l setCornerRadius:10.0];

Answer 2

You could use a category for UIImage which is an alternate way to subclass a Class and sometimes easier for just small changes.

e.g add a method that returns a UIImage with the rounded corner attributes set.

+(UIImage *)imageWithContentsOfFile:(NSString *)file cornerRadius:(NSInteger)... 

more info on Objective-c categories can be found http://macdevelopertips.com/objective-c/objective-c-categories.html

Answer 3

Rather than subclassing, you can achieve more powerful functionality through simple categories on UIImageView and CALayer.

Create a category on UIImageView like this:

- (void)maskRoundCorners:(UIRectCorner)corners radius:(CGFloat)radius {
    // To round all corners, we can just set the radius on the layer
    if ( corners == UIRectCornerAllCorners ) {
        self.layer.cornerRadius = radius;
        self.layer.masksToBounds = YES;
    } else {
        // If we want to choose which corners we want to mask then
        // it is necessary to create a mask layer.
        self.layer.mask = [CALayer maskLayerWithCorners:corners radii:CGSizeMake(radius, radius) frame:self.bounds];
    }
}

This calls a category method on CALayer:

+ (id)maskLayerWithCorners:(UIRectCorner)corners radii:(CGSize)radii frame:(CGRect)frame {

    // Create a CAShapeLayer
    CAShapeLayer *mask = [CAShapeLayer layer];

    // Set the frame
    mask.frame = frame;

    // Set the CGPath from a UIBezierPath
    mask.path = [UIBezierPath bezierPathWithRoundedRect:mask.bounds byRoundingCorners:corners cornerRadii:radii].CGPath;

    // Set the fill color
    mask.fillColor = [UIColor whiteColor].CGColor;

    return mask;
}

So, this allows you to round any combination (see UIRectCorner) of corners, which is especially handy if you want to put an image in a group style UITableView. There is one caveat when doing this however. Because we've not subclassed UIImageView, we cannot inject any code into layoutSubviews, which means that the mask layer may not be correct. In fact, when configuring cells, the bounds of the image view won't even be set when you call the category method. Hence, you need to ensure the bounds of the image view is set before adding rounded corners (except if using UIRectCornersAllCorners).

Here is some code which does this:

        // Perform corner rounding
        UIRectCorner corners = !UIRectCornerAllCorners;
        if (indexPath.row == 0) 
            corners = UIRectCornerTopLeft;
        if (indexPath.row == numberOfRowsInTheTable)  
            corners |= UIRectCornerBottomLeft;

        if (corners > 0) {
            cell.imageView.bounds = CGRectMake(0.f, 0.f, [self.tableView rowHeight], [self.tableView rowHeight]);
            [cell.imageView maskRoundCorners:corners radius:10.f];
        } else {
            [cell.imageView removeRoundCornersMask];
        }

I have another category which removes rounded corners - all that does is remove any masks and set the cornerRadius to 0.

Answer 4

Yes, you should subclass UIImageView, and use your custom subclass throughout your project.