iPhone UIImageView in UIScrollView not zooming to center

Question

I have a UIImageView inside a UIScrollView so I can allow zooming, the zooming works but it doesn't keep the UIImageView centered and ends up cutting off the bottom of the image and leaves black space on top.

This is what I have:

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.

    scroller.bouncesZoom   = YES;
    scroller.clipsToBounds = YES;

    float scale = image.size.width/320;
    UIImage *scaled = [UIImage imageWithCGImage:[image CGImage] scale:scale orientation:UIImageOrientationUp];

    imageView = [[UIImageView alloc] initWithImage:scaled];
    imageView.userInteractionEnabled = YES;
    [imageView setCenter:CGPointMake(160,240)];

    [scroller addSubview:imageView];
    scroller.contentSize = [imageView frame].size;

    scroller.maximumZoomScale = 4.0;
    scroller.minimumZoomScale = 1.0;
    scroller.zoomScale        = 1.0;
}

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
    return imageView;
}

Any suggestions?

There was a talk on designing Scroll Views in last year's WWDC. Have a look at it, it really helped me a lot :) — Julian, Jun 22 '11 at 19:34

score 0 · Answer 1 · answered Mar 21 '14 at 05:28

0

If pagination is not needed then disable pagination it works fine

scrollview.pagingEnabled = NO;

answered Mar 21 '14 at 05:28

Nagaraj

802
9
11

score 0 · Answer 2 · answered Jun 22 '11 at 19:37

0

I think this is what you want.

answered Jun 22 '11 at 19:37

500865

6,920
7
44
87

this is what i want, but i guess there's no way to do without overriding – thechengster Jun 23 '11 at 12:40

score -1 · Answer 3 · answered Jun 22 '11 at 19:35

Below is the code I've used in my app (adapted from the WWDC sample) Maybe you can take something out of it :)

    CGSize imageSize =[image size];
    CGSize boundsSize = scrollview.bounds.size;
    CGRect frameToCenter = imageview.frame;

    // center horizontally
    if (frameToCenter.size.width < boundsSize.width)
        frameToCenter.origin.x = (boundsSize.width - frameToCenter.size.width) / 2;
    else
        frameToCenter.origin.x = 0;

    // center vertically
    if (frameToCenter.size.height < boundsSize.height)
        frameToCenter.origin.y = (boundsSize.height - frameToCenter.size.height) / 2;
    else
        frameToCenter.origin.y = 0;

    imageview.frame = frameToCenter;

    CGFloat xScale = boundsSize.width / imageSize.width;    // the scale needed to perfectly fit the image width-wise
    CGFloat yScale = boundsSize.height / imageSize.height;  // the scale needed to perfectly fit the image height-wise
    CGFloat minScale = MIN(xScale, yScale);                 // use minimum of these to allow the image to become fully visible

    // on high resolution screens we have double the pixel density, so we will be seeing every pixel if we limit the
    // maximum zoom scale to 0.5.
    CGFloat maxScale = 1.0 / [[UIScreen mainScreen] scale];

    // don't let minScale exceed maxScale. (If the image is smaller than the screen, we don't want to force it to be zoomed.) 
    if (minScale > maxScale) {
        minScale = maxScale;
    }

    scrollview.contentSize=imageSize;
    scrollview.maximumZoomScale=maxScale;
    scrollview.minimumZoomScale=minScale;
    scrollview.zoomScale=1;

iPhone UIImageView in UIScrollView not zooming to center

3 Answers3