Use CGPoint in SWIFT 3 to get pixel color from the image

class PixelExtractor: NSObject {

let image: CGImage
let context: CGContextRef?

var width: Int {
 get {
 return CGImageGetWidth(image)
 }
}

var height: Int {
 get {
 return CGImageGetHeight(image)
 }
}

init(img: CGImage) {
 image = img
 context = PixelExtractor. createBitmapContext(img)
}

class func createBitmapContext(img: CGImage) -> CGContextRef {

 // Get image width, height
 let pixelsWide = CGImageGetWidth(img)
 let pixelsHigh = CGImageGetHeight(img)

 let bitmapBytesPerRow = pixelsWide * 4
 let bitmapByteCount = bitmapBytesPerRow * Int(pixelsHigh)

 // Use the generic RGB color space.
 let colorSpace = CGCol orSpaceCreateDeviceRGB()

 // Allocate memory for image data. This is the destination in memory
 // where any drawing to the bitmap context will be rendered.
 let bitmapData = malloc (bitmapByteCount)
 let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedFirst.rawValue)
 let size = CGSizeMake(CGFloat(pixelsWide), CGFloat(pixelsHigh))
 UIGraphicsBeginImageContextWithOptions(size, false, 0.0 )
 // create bitmap
 let context = CGBitmapContextCreate(bitmapData, pixelsWide, pixelsHigh, 8,
 bitmapBytesPerRow, colorSpace, bitmapInfo.rawValue)

 // draw the image onto the context
 let rect = CGRect(x: 0, y: 0, width: pixelsWide, height: pixelsHigh)
 CGContextDrawImage(context, rect, img)

 return context!
}

func colorAt(xx: Int, y: Int)->UIColor {

 assert(0<=x && x assert(0<=y && y
 let uncas tedData = CGBitmapContextGetData(context)
 let data = UnsafePointer(uncastedData)

 let offset = 4 * (y * width + x)

 let alpha : UInt8 = data[offset]
 let red: UInt8 = data[offset+1]
 let green: UInt8 = data[offset+2]
 let blue: UInt8 = data[offset+ 3]

 let color = UIColor(red: CGFloat(red)/255.0, green: CGFloat(green)/255.0, blue: CGFloat(blue)/255.0, alpha: CGFloat(alpha)/255.0 )

 return color
}

let data = UnsafePointer(uncastedData)

let data = UnsafeRawPointer(uncastedData)

let alpha = data.load(fromByteOffset: offset, as: UInt8.self)
 let red = data.load(fromByteOffset: offset+1, as: UInt8 .self)
 let green = data.load(fromByteOffset: offset+2, as: UInt8.self)
 let blue = data.load(fromByteOffset: offset+3, as: UInt8.self)< /pre> 
Alternatively, you can get UnsafeMutablePointer from your uncastedData (assuming it is an UnsafeMutableRawPointer):
 
 
let data = uncastedData.assumingMemoryBound(to: UInt8.self)

I tried this PixelExtractor class in Swift 3 and got an error;
Cannot call the type with the parameter list of type'(UnsafeMutableRawPointer?)' Initial value setting item of'UnsafePointer'

class PixelExtractor: NSObject {

let image: CGImage
let context: CGContextRef?

var width: Int {
 get {
 return CGImageGetWidth(image)
 }
}

var height : Int {
 get {
 return CGImag eGetHeight(image)
 }
}

init(img: CGImage) {
 image = img
 context = PixelExtractor.createBitmapContext(img)
}

class func createBitmapContext(img: CGImage) -> CGContextRef {

 // Get image width, height
 let pixelsWide = CGImageGetWidth(img)< br /> let pixelsHigh = CGImageGetHeight(img)

 let bitmapBytesPerRow = pixelsWide * 4
 let bitmapByteCount = bitmapBytesPerRow * Int(pixelsHigh)

 // Use the generic RGB color space.
 let colorSpace = CGColorSpaceCreateDeviceRGB()

 // Allocate memory for image data. This is the destination in memory
 // where any drawing to the bitmap context will be rendered.
 let bitmapData = malloc(bitmapByteCount)
 let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedFirst.rawValue)
 let size = CGSizeMake(CGFloat(pixelsWide), CGFloat(pixelsHigh)) 
 UIGraphicsBeginImageCon textWithOptions(size, false, 0.0)
 // create bitmap
 let context = CGBitmapContextCreate(bitmapData, pixelsWide, pixelsHigh, 8,
 bitmapBytesPerRow, colorSpace, bitmapInfo.rawValue)
< br /> // draw the image onto the context
 let rect = CGRect(x: 0, y: 0, width: pixelsWide, height: pixelsHigh)
 CGContextDrawImage(context, rect, img)

 return context!
}

func colorAt(xx: Int, y: Int)->UIColor {

 assert(0<= x && x assert(0<=y && y
 let uncastedData = CGBitmapContextGetData(context)
 let data = UnsafePointer(uncastedData) 

 let offset = 4 * (y * width + x)

 let alpha: UInt8 = data[offset]
 let red: UInt8 = data[offset+ 1]
 let green: UInt8 = data[offset+2]
 let blue: UInt8 = data[offset+3]

 let color = UIColor(red: CGFloat(red )/255.0, green: CGFloat(green)/255.0, blue: CGFloat(blue)/255. 0, alpha: CGFloat(alpha)/255.0)

 return color
}

}

Fix this error.

< p>

let data = UnsafePointer(uncastedData)

– >

let data = UnsafeRawPointer(uncastedData)< /pre> 
Get other errors;'Enter' UnsafeRawPointer? ’No subscript member’
 
How to fix this error? 
When your data contains UnsafeRawPointer, you can write something similar: 
 
 
let alpha = data.load(fromByteOffset: offset, as: UInt8.self)
 let red = data.load(fromByteOffset: offset+1, as: UInt8.self)
 let green = data. load(fromByteOffset: offset+2, as: UInt8.self)
 let blue = data.load(fromByteOffset: offset+3, as: UInt8.self)
Or, you can get UnsafeMutablePointer  from your uncastedData (assuming it is an UnsafeMutableRawPointer):

let data = uncastedData.assumingMemoryBound(to: UInt8.self)