A card zooming custom flow layout

ZoomCardFlowLayout.swift

//
//  ZoomCardFlowLayout.swift
//  
//
//  Created by Oni_01 on 12/05/15.
//  Copyright (c) 2015 Andrea Altea. All rights reserved.
//

import UIKit

class ZoomCardFlowLayout: UICollectionViewFlowLayout {
    
    override init() {
        super.init();
        
        setLayout();
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder);
        
        setLayout();
    }
    
    func setLayout() {
        self.minimumInteritemSpacing = 0;
        self.minimumLineSpacing = 0;
        self.scrollDirection = UICollectionViewScrollDirection.Horizontal;
        self.sectionInset = UIEdgeInsetsMake(0, 38, 0, 38); //UIEdgeInsetsMake(15, 38, 10, 38);
        
    }
    
    override func prepareLayout() {
        super.prepareLayout();
        
        //Get Visible index paths
        if let indexPaths = self.collectionView?.indexPathsForVisibleItems() {
            //CollectionView Center
            let center = self.collectionView?.center;
            
            for obj in indexPaths {
                let indexPath = obj as! NSIndexPath;
                if let cell = self.collectionView?.cellForItemAtIndexPath(indexPath) {
                    
                    //Get Cell Center in CollectionView and calculate distance
                    let cellCenter = self.collectionView!.convertPoint(cell.center, fromCoordinateSpace: self.collectionView!);
                    let contentOffset = self.collectionView!.contentOffset.x;
                    let xDistance = fabsf(Float(center!.x - cellCenter.x + contentOffset));
                    
                    //Scale Factor based on view width
                    var scale = 1 - CGFloat(xDistance / 1000.0 /*multiplier*/);
                    scale = scale > 1 ? 1 : scale;
                    scale = scale < 0.85 ? 0.85 : scale;
                    
                    cell.transform = CGAffineTransformMakeScale(scale, scale);
                    
                    //Added shadow Effect
                    cell.layer.shadowRadius = (93.75 * (scale * scale)) - 73.75 * scale;
                    cell.layer.shadowOffset = CGSizeMake(0, 4.0 * scale);
                }
            }
        }
    }
    
    override func collectionViewContentSize() -> CGSize {
        var size = super.collectionViewContentSize();
        
        if let view = self.collectionView {
            let height = view.bounds.height - view.contentInset.top - view.contentInset.bottom;
            size.height = height;
        }
        
        return size;
        
    }
    
    override func shouldInvalidateLayoutForBoundsChange(newBounds: CGRect) -> Bool {
        return true;
    }
    
    //MARK: - Pagination

    override func targetContentOffsetForProposedContentOffset(proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint {
        if let attributes = self.layoutAttributesForElementsInRect(self.collectionView!.bounds) {
            if attributes.count == 0 {
                
                return proposedContentOffset;
            } else {
                
                var candidate = attributes.first!;
                
                for attribute in attributes {
                        if attribute.representedElementCategory != .Cell {
                            continue;
                        }
                        
                        if (velocity.x > 0.0 && attribute.center.x > candidate.center.x) ||
                            (velocity.x <= 0.0 && attribute.center.x < candidate.center.x) {
                                candidate = attribute;
                        }
                }
                
                return CGPointMake(candidate.center.x - self.collectionView!.bounds.size.width * 0.5,
                    proposedContentOffset.y);
            }
        }
        
        return CGPointZero;
    }
}