Scrolling an image continuosly
- (void)viewDidLoad {
        [super viewDidLoad];

        // add the last image (image4) into the first position
        [self addImageWithName:@"image4.jpg" atPosition:0];

        // add all of the images to the scroll view
        for (int i = 1; i < 5; i++) {
            [self addImageWithName:[NSString stringWithFormat:@"image%i.jpg",i] atPosition:i];
        }

        // add the first image (image1) into the last position
        [self addImageWithName:@"image1.jpg" atPosition:5];

        scrollView.contentSize = CGSizeMake(320, 2496);
        [scrollView scrollRectToVisible:CGRectMake(0,416,320,416) animated:NO];
    }

    - (void)addImageWithName:(NSString*)imageString atPosition:(int)position {
        // add image to scroll view
        UIImage *image = [UIImage imageNamed:imageString];
        UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
        imageView.frame = CGRectMake(0,position*416,320, 416);
        [scrollView addSubview:imageView];
        [imageView release];
    }

- (void)scrollViewDidEndDecelerating:(UIScrollView *)sender {
    NSLog(@"%f",scrollView.contentOffset.y);
    // The key is repositioning without animation
    if (scrollView.contentOffset.y == 0) {
        // user is scrolling to the left from image 1 to image 4
        // reposition offset to show image 4 that is on the right in the scroll view
        [scrollView scrollRectToVisible:CGRectMake(0,1664,320,416) animated:NO];
    }
    else if (scrollView.contentOffset.y == 2080) {
        // user is scrolling to the right from image 4 to image 1
        // reposition offset to show image 1 that is on the left in the scroll view
        [scrollView scrollRectToVisible:CGRectMake(0,416,320,416) animated:NO];
    }
}