Setting Corner Radius on UIImageView not working

Question

You need to set the layer's masksToBounds property to YES:

cell.previewImage.layer.masksToBounds = YES;

This is because the UIImageView control creates a pseudo-subview to hold the UIImage object.

Also worth noting that

1. If you are using aspectFit AND cornerRadius with clipsToBounds/masksToBounds, you won't get the rounded corners.

i.e if you have this

theImageView.contentMode = .scaleAspectFit

and

   theImageView.layer.cornerRadius = (theImageView.frame.size.height)/2
    theImageView.clipsToBounds = true

or

theImageView.layer.masksToBounds = true

It won't work. you will have to get rid of aspectFit code

//theImageView.contentMode = .scaleAspectFit

2. Make sure the width and the height for the Image View is same

This should work

cell.previewImage.clipsToBounds = YES;

cell.previewImage.layer.cornerRadius = 20;

I believe you need to set:

cell.previewImage.layer.masksToBounds = YES;
cell.previewImage.layer.opaque = NO;

In Xcode Interface Builder, selecting 'Clip Subviews' Drawing attribute for the view together with setting the corner radius in the code cell.previewImage.layer.cornerRadius = 20;does the job for me!

See 'Clip Subviews' option in IB

Try this below piece of code

cell.previewImage.layer.cornerRadius = 20;
cell.previewImage.clipsToBounds = YES;