How to Zoom a Uiscrollview Inside of a Uicollectionviewcell

How to zoom a UIScrollView inside of a UICollectionViewCell?

You might want to try manipulating the UIGestureRecognizers in order to do that. In the GalleryViewController:

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView 
                  cellForItemAtIndexPath:(NSIndexPath *)indexPath {

    GalleryImageCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"galleryImageCell" forIndexPath:indexPath];

    ImageContext *imageContext = [self.images objectAtIndex:indexPath.row];

    cell.imageContext = imageContext;
    [self.collectionView addGestureRecognizer:cell.scrollView.pinchGestureRecognizer];
    [self.collectionView addGestureRecognizer:cell.scrollView.panGestureRecognizer];

    return cell;
}

From Apple's documentation on UIView:

Attaching a gesture recognizer to a view defines the scope of the represented gesture, causing it to receive touches hit-tested to that view and all of its subviews. The view retains the gesture recognizer.

So you'll also want to make sure to remove them when the cell is not showing anymore.

- (void)collectionView:(UICollectionView *)collectionView 
  didEndDisplayingCell:(UICollectionViewCell *)cell 
    forItemAtIndexPath:(NSIndexPath *)indexPath {

    // Get the cell instance and ...
    [self.collectionView removeGestureRecognizer:cell.scrollView.pinchGestureRecognizer];
    [self.collectionView removeGestureRecognizer:cell.scrollView.panGestureRecognizer];
}

Since you're not modifying the UIGestureRecognizer's delegate, only its scope, it will still control the zooming of just that cell's scrollview.

EDIT:

I added the panGestureRecognizer to the above examples, following a suggestion from the OP that it was needed. The zooming itself is completely handled by the pinchGestureRecognizer, but it's true that in most cases, after zooming an image to a point where only a subset of it is visible, you'll want to pan to move the visible portion around. That is, it's part of a proper zooming experience.

Zoomed UIImage inside ScrollView inside CollectionViewCell

Create UICollectionViewCell subclass with xib

Subclassing UICollectionViewCell and initialising from xib

or without xib

http://randexdev.com/2014/08/uicollectionviewcell/

then set delegate for scrollView is collectionViewCell subclass

Add UIScrollViewDelegate code to cell

You can access imageView from cell property

Reset Scrollview in UICollectionViewCell after scrolling

you need to implement this method: https://developer.apple.com/documentation/uikit/uicollectionviewdelegate/1618087-collectionview
and zoom out the scrollView before displaying the cell. This method will handle your case. Happy coding ;)

func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath)

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