Roundtrip a UIImage to its raw pixel values and back to an image again

imageRoundtrip.swift

import UIKit
import CoreGraphics

func imageFromPixelValues(pixelValues: [UInt8]?, width: Int, height: Int) -> CGImage?
{
    var imageRef: CGImage?
    if pixelValues != nil {
        let imageDataPointer = UnsafeMutablePointer<UInt8>(pixelValues!)

        let colorSpaceRef = CGColorSpaceCreateDeviceGray()

        let bitsPerComponent = 8
        let bytesPerPixel = 1
        let bitsPerPixel = bytesPerPixel * bitsPerComponent
        let bytesPerRow = bytesPerPixel * width
        let totalBytes = height * bytesPerRow

        let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.None.rawValue)
            .union(.ByteOrderDefault)
        let providerRef = CGDataProviderCreateWithData(nil, imageDataPointer, totalBytes, nil)
        imageRef = CGImageCreate(width,
            height,
            bitsPerComponent,
            bitsPerPixel,
            bytesPerRow,
            colorSpaceRef,
            bitmapInfo,
            providerRef,
            nil,
            false,
            CGColorRenderingIntent.RenderingIntentDefault)
    }

    return imageRef
}

func pixelValuesFromImage(imageRef: CGImage?) -> ([UInt8]?, width: Int, height: Int)
{
    var width = 0
    var height = 0
    var pixelValues: [UInt8]?
    if imageRef != nil {
        width = CGImageGetWidth(imageRef)
        height = CGImageGetHeight(imageRef)
        let bitsPerComponent = CGImageGetBitsPerComponent(imageRef)
        let bytesPerRow = CGImageGetBytesPerRow(imageRef)
        let totalBytes = height * bytesPerRow

        let colorSpace = CGColorSpaceCreateDeviceGray()
//        let colorSpace = CGColorSpaceCreateDeviceRGB()
        let buffer = [UInt8](count: totalBytes, repeatedValue: 0)
        let mutablePointer = UnsafeMutablePointer<UInt8>(buffer)

        let contextRef = CGBitmapContextCreate(mutablePointer, width, height, bitsPerComponent, bytesPerRow, colorSpace, 0)
        CGContextDrawImage(contextRef, CGRectMake(0.0, 0.0, CGFloat(width), CGFloat(height)), imageRef)

        let bufferPointer = UnsafeBufferPointer<UInt8>(start: mutablePointer, count: totalBytes)
        pixelValues = Array<UInt8>(bufferPointer)
    }

    return (pixelValues, width, height)
}

var image: UIImage? = nil
let URL = NSBundle.mainBundle().URLForResource("zebra_5", withExtension: "tif")
let path = URL?.path
if (path != nil && NSFileManager().fileExistsAtPath(path!)) {
    do {
        try NSData(contentsOfURL: URL!, options: .DataReadingMappedIfSafe)
    } catch let error as NSError {
        print ("Error: \(error.localizedDescription)")
    }
    image = UIImage(contentsOfFile: path!)
}

let (intensityValues, width, height) = pixelValuesFromImage(image?.CGImage)
let roundTrippedImage = imageFromPixelValues(intensityValues, width: width, height: height)
let zebra = UIImage(CGImage: roundTrippedImage!)

swift 3+

 let data: [UInt8] = [...]
 let image = UIImage(data: Data(bytes: data, count: data.count))

 guard let dataPng: Data = pngData() else { return [] }
 let finalData = [UInt8](dataPng)