IOS: UIImageView border white with radius display a strange dark line in 4 corners

Question

I set the border white and radius for my ImageView. But in 4 corner of the ImageView, some dark line appear.
Here is the code I set the color

Answer 1

i tried this function written in imageview category:

- (void)setBorderWithRounCornersWithColor:(UIColor *)color{

    self.layer.cornerRadius = 5.0f;
    self.layer.masksToBounds = YES;

    if(color){

        self.layer.borderColor=color.CGColor;
        self.layer.borderWidth=1.0f;
    }

}

at time of using:

[self.imageView setBorderWithRounCornersWithColor:nil];