Answer in reference to Stack Overflow question: http://stackoverflow.com/questions/18614536/how-to-create-uiscrollview-with-custom-shapes-in-ios

gistfile1.m

#define IMAGE_WIDTH 100.0
#define IMAGE_HEIGHT 100.0

@implementation SOMaskScrollView

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        self.backgroundColor = [UIColor whiteColor];
        // Initialization code
        
    }
    return self;
}


- (void)layoutSubviews {
    UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:self.frame];
    CGFloat totalImages = 20;
    UIImage *repeatImage = [UIImage imageNamed:@"stripe_black.png"];
    scrollView.contentSize = CGSizeMake(self.frame.size.width, totalImages*IMAGE_HEIGHT);
    for (int count = 0; count < totalImages; count++) {
        UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, count*IMAGE_HEIGHT, IMAGE_WIDTH, IMAGE_HEIGHT)];
        imageView.image = repeatImage;
        [scrollView addSubview:imageView];
    }
    [self addSubview:scrollView];
    
    CAShapeLayer *maskLayer = [CAShapeLayer layer];
    maskLayer.path = [UIBezierPath bezierPathWithRoundedRect:CGRectInset(self.frame, 5, 5) cornerRadius:50.0f].CGPath;
    self.layer.mask = maskLayer;
}

@end