Swift Image Resizer

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 {
    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
}

You should change this:
UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)

to this:
UIGraphicsBeginImageContextWithOptions(newSize, false, UIScreen.mainScreen().scale)

for the best quality on iPhone 6+

Thank you ! :)

Awesome! Thank you! 😄

Thanks to the original author and thanks to @bashome for the fix. Really works now.

Updated for Swift 2.0:
https://gist.github.com/iroller/390f4e20736db3bc39a0

thanks for you help me!

Thanks for posting this. Don't know why UIKit doesn't have a method for this.

Updated for use as a UIImage Extension
https://gist.github.com/justinlevi/ee037a4bb63598f6e56f

How do I implement this into my app?

Very useful! Awesome!

Thank you