Swift replacement for UIImage+PDF

PDFImage.swift

//
//  PDFImage.swift. Copyright © 2016 Nigel Timothy Barber (@mindbrix). All rights reserved.
//
import UIKit

extension UIImage {
    static func PDFImageWith(url: NSURL, pageNumber: Int, width: CGFloat) -> UIImage? {
        return PDFImageWith(url, pageNumber: pageNumber, constraints: CGSizeMake(width, 0))
    }
    
    static func PDFImageWith(url: NSURL, pageNumber: Int, height: CGFloat) -> UIImage? {
        return PDFImageWith(url, pageNumber: pageNumber, constraints: CGSizeMake(0, height))
    }
    
    static func PDFImageWith(url: NSURL, pageNumber: Int) -> UIImage? {
        return PDFImageWith(url, pageNumber: pageNumber, constraints: CGSizeMake(0, 0))
    }
    
    static func PDFImageWith(url: NSURL, pageNumber: Int, constraints: CGSize) -> UIImage? {
        if let pdf = CGPDFDocumentCreateWithURL(url) {
            if let page = CGPDFDocumentGetPage(pdf, pageNumber) {
                let size = CGPDFPageGetBoxRect(page, .MediaBox).size.forConstraints(constraints)
                let cacheURL = url.PDFImageCacheURL(pageNumber, size: size)
                
                if let url = cacheURL {
                    if NSFileManager.defaultManager().fileExistsAtPath(url.path!) {
                        if let image = UIImage(contentsOfFile: url.path!) {
                            return UIImage(CGImage: image.CGImage!, scale: UIScreen.mainScreen().scale, orientation: .Up)
                        }
                    }
                }
                
                UIGraphicsBeginImageContextWithOptions(size, false, UIScreen.mainScreen().scale)
                if let ctx = UIGraphicsGetCurrentContext() {
                    CGContextConcatCTM(ctx, CGAffineTransformMake(1, 0, 0, -1, 0, size.height))
                    CGContextConcatCTM(ctx, CGPDFPageGetDrawingTransform(page, .MediaBox, CGRectMake(0, 0, size.width, size.height), 0, true))
                    CGContextDrawPDFPage(ctx, page)
                    let image = UIGraphicsGetImageFromCurrentImageContext()
                    
                    if let url = cacheURL {
                        if let imageData = UIImagePNGRepresentation(image) {
                            imageData.writeToFile(url.path!, atomically:false)
                        }
                    }
                    return UIImage(CGImage: image.CGImage!, scale: UIScreen.mainScreen().scale, orientation: .Up)
                }
            }
        }
        return nil
    }    
}

extension CGSize {
    func forConstraints(constraints: CGSize) -> CGSize {
        if constraints.width == 0 && constraints.height == 0 {
            return self
        }
        let sx = constraints.width / width, sy = constraints.height / height
        let s = sx != 0 && sy != 0 ? min(sx, sy) : max(sx, sy)
        return CGSizeMake(ceil(width * s), ceil(height * s))
    }
}

extension NSURL {
    func PDFImageCacheURL(pageNumber: Int, size: CGSize) -> NSURL? {
        if let path = self.path {
            do {
                let attributes = try NSFileManager.defaultManager().attributesOfItemAtPath(path)
                
                if let fileSize = attributes[NSFileSize] as! NSNumber? {
                    if let fileDate = attributes[NSFileModificationDate] as! NSDate? {
                        let hashables = path + fileSize.stringValue + String(fileDate.timeIntervalSince1970) + String(size)
                        
                        let cacheDirectory = NSSearchPathForDirectoriesInDomains(.CachesDirectory, .UserDomainMask, true)[0] + "/__PDF_CACHE__"
                        do {
                            try NSFileManager.defaultManager().createDirectoryAtPath(cacheDirectory, withIntermediateDirectories: true, attributes:nil)
                            
                        } catch {}
                        
                        return NSURL(fileURLWithPath: cacheDirectory + "/" + String(format:"%2X", hashables.hash) + ".png")
                    }
                }
            } catch {}
        }
        return nil
    }
}