README.md

iOS Parallax effect on images of UITableViewCell

The goal of this project is to create a parallax effect on a UIImageView on a UITableViewCell when the table scrolls.

This code has been created originally to provide a parallax effect on meets's discover tab.

Download the app and test it for free! Feedback is welcome!

Documentation

On your UITableViewCell

1. Put the parallaxImageView inside a UIView with clipsToBounds = YES; with some offest.
2. Add this function to calculate the image offset when the UITableView scrolls.

- (void)cellOnTableView:(UITableView *)tableView didScrollOnView:(UIView *)view
{
    CGRect rectInSuperview = [tableView convertRect:self.frame toView:view];
    
    float distanceFromCenter = CGRectGetHeight(view.frame)/2 - CGRectGetMinY(rectInSuperview);
    float difference = CGRectGetHeight(self.parallaxImage.frame) - CGRectGetHeight(self.frame);
    float move = (distanceFromCenter / CGRectGetHeight(view.frame)) * difference;
    
    CGRect imageRect = self.parallaxImage.frame;
    imageRect.origin.y = -(difference/2)+move;
    self.parallaxImage.frame = imageRect;
}

On your UITableViewDelegate add this function.

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    // Get visible cells on table view.
    NSArray *visibleCells = [self.tableView visibleCells];

    for (JBParallaxCell *cell in visibleCells) {
        [cell cellOnTableView:self.tableView didScrollOnView:self.view];
    }
}

And that is all, you can use the demo project to see how everithig works together.

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