RBResizer.swift

//
//  RBResizer.swift
//  Locker
//
//  Created by Hampton Catlin on 6/20/14.
//  Copyright (c) 2014 rarebit. All rights reserved.
//

import UIKit

func RBSquareImageTo(image: UIImage, size: CGSize) -> UIImage? {
    return RBResizeImage(RBSquareImage(image), size)
}

func RBSquareImage(image: UIImage) -> UIImage? {
    var originalWidth  = image.size.width
    var originalHeight = image.size.height
    
    var edge: CGFloat
    if originalWidth > originalHeight {
        edge = originalHeight
    } else {
        edge = originalWidth
    }
    
    var posX = (originalWidth  - edge) / 2.0
    var posY = (originalHeight - edge) / 2.0
    
    var cropSquare = CGRectMake(posX, posY, edge, edge)
    
    var imageRef = CGImageCreateWithImageInRect(image.CGImage, cropSquare);
    return UIImage(CGImage: imageRef, scale: UIScreen.mainScreen().scale, orientation: image.imageOrientation)
}

func RBResizeImage(image: UIImage?, targetSize: CGSize) -> UIImage? {
    if let image = image {
        let size = image.size
        
        let widthRatio  = targetSize.width  / image.size.width
        let heightRatio = targetSize.height / image.size.height
        
        // Figure out what our orientation is, and use that to form the rectangle
        var newSize: CGSize
        if(widthRatio > heightRatio) {
            newSize = CGSizeMake(size.width * heightRatio, size.height * heightRatio)
        } else {
            newSize = CGSizeMake(size.width * widthRatio,  size.height * widthRatio)
        }
        
        // This is the rect that we've calculated out and this is what is actually used below
        let rect = CGRectMake(0, 0, newSize.width, newSize.height)
        
        // Actually do the resizing to the rect using the ImageContext stuff
        UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
        image.drawInRect(rect)
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        return newImage
    } else {
        return nil
    }
}

updated to work with swift 1.1

I don't know why it doesn't work for me. Example: my origin image size is 480x640, so cropSquare is 480x480, but instead of getting same size for imageRef, I'm getting 480x400, and then function is returning "img" with size 200x240 (?!). But if I use 0 instead of posY in CGRectMake (posX, 0, edge, edge) everything is fine (returning image size is 480x480), but the image is not centered but is cropped from the top, of course. Can someone help me?

markotl88, take a look at this comment section :
https://gist.github.com/hcatlin/180e81cd961573e3c54d

How do I make this work? How do I use it?