CGDataProvider returning null in Swift 4 - ios

Question

I'm trying to fix a problem in SwiftColorPicker (by Matthias Schlemm) that popped up with Swift 4.0. I'm going to include the whole PickerImage class, so you can see the full context.
import UIKit
import ImageIO
open class PickerImage {
var provider:CGDataProvider!
var imageSource:CGImageSource?
var image:UIImage?
var mutableData:CFMutableData
var width:Int
var height:Int
fileprivate func createImageFromData(_ width:Int, height:Int) {
let colorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedFirst.rawValue)
let provider = CGDataProvider(data: mutableData)
imageSource = CGImageSourceCreateWithDataProvider(provider!, nil)
let cgimg = CGImage(width: Int(width), height: Int(height), bitsPerComponent: Int(8), bitsPerPixel: Int(32), bytesPerRow: Int(width) * Int(4),
space: colorSpace, bitmapInfo: bitmapInfo, provider: provider!, decode: nil, shouldInterpolate: true, intent: CGColorRenderingIntent.defaultIntent)
image = UIImage(cgImage: cgimg!)
}
func changeSize(_ width:Int, height:Int) {
self.width = width
self.height = height
let size:Int = width * height * 4
CFDataSetLength(mutableData, size)
createImageFromData(width, height: height)
}
init(width:Int, height:Int) {
self.width = width
self.height = height
let size:Int = width * height * 4
mutableData = CFDataCreateMutable(kCFAllocatorDefault, size)
createImageFromData(width, height: height)
}
open func writeColorData(_ h:CGFloat, a:CGFloat) {
let d = CFDataGetMutableBytePtr(self.mutableData)
if width == 0 || height == 0 {
return
}
var i:Int = 0
let h360:CGFloat = ((h == 1 ? 0 : h) * 360) / 60.0
let sector:Int = Int(floor(h360))
let f:CGFloat = h360 - CGFloat(sector)
let f1:CGFloat = 1.0 - f
var p:CGFloat = 0.0
var q:CGFloat = 0.0
var t:CGFloat = 0.0
let sd:CGFloat = 1.0 / CGFloat(width)
let vd:CGFloat = 1 / CGFloat(height)
var double_s:CGFloat = 0
var pf:CGFloat = 0
let v_range = 0..<height
let s_range = 0..<width
for v in v_range {
pf = 255 * CGFloat(v) * vd
for s in s_range {
i = (v * width + s) * 4
d?[i] = UInt8(255)
if s == 0 {
q = pf
d?[i+1] = UInt8(q)
d?[i+2] = UInt8(q)
d?[i+3] = UInt8(q)
continue
}
double_s = CGFloat(s) * sd
p = pf * (1.0 - double_s)
q = pf * (1.0 - double_s * f)
t = pf * ( 1.0 - double_s * f1)
switch(sector) {
case 0:
d?[i+1] = UInt8(pf)
d?[i+2] = UInt8(t)
d?[i+3] = UInt8(p)
case 1:
d?[i+1] = UInt8(q)
d?[i+2] = UInt8(pf)
d?[i+3] = UInt8(p)
case 2:
d?[i+1] = UInt8(p)
d?[i+2] = UInt8(pf)
d?[i+3] = UInt8(t)
case 3:
d?[i+1] = UInt8(p)
d?[i+2] = UInt8(q)
d?[i+3] = UInt8(pf)
case 4:
d?[i+1] = UInt8(t)
d?[i+2] = UInt8(p)
d?[i+3] = UInt8(pf)
default:
d?[i+1] = UInt8(pf)
d?[i+2] = UInt8(p)
d?[i+3] = UInt8(q)
}
}
}
}
}
In createImageFromData, the line
let provider = CGDataProvider(data: mutableData)
is returning a nil value, which, of course, causes the following line to crash. This was working fine in Swift 3.
Here are the values in debugger:
Dealing with memory allocation is a bit beyond my current skillset, so I'm struggling with what's actually going on here. Has anything related to this changed in Swift 4.0 that would cause the CGDataProvider call to return a nil value?
Edit:
Here is the ColorPicker class that initializes the PickerImage objects.
import UIKit
import ImageIO
open class ColorPicker: UIView {
fileprivate var pickerImage1:PickerImage?
fileprivate var pickerImage2:PickerImage?
fileprivate var image:UIImage?
fileprivate var data1Shown = false
fileprivate lazy var opQueue:OperationQueue = {return OperationQueue()}()
fileprivate var lock:NSLock = NSLock()
fileprivate var rerender = false
open var onColorChange:((_ color:UIColor, _ finished:Bool)->Void)? = nil
open var a:CGFloat = 1 {
didSet {
if a < 0 || a > 1 {
a = max(0, min(1, a))
}
}
}
open var h:CGFloat = 0 { // // [0,1]
didSet {
if h > 1 || h < 0 {
h = max(0, min(1, h))
}
renderBitmap()
setNeedsDisplay()
}
}
fileprivate var currentPoint:CGPoint = CGPoint.zero
open func saturationFromCurrentPoint() -> CGFloat {
return (1 / bounds.width) * currentPoint.x
}
open func brigthnessFromCurrentPoint() -> CGFloat {
return (1 / bounds.height) * currentPoint.y
}
open var color:UIColor {
set(value) {
var hue:CGFloat = 1
var saturation:CGFloat = 1
var brightness:CGFloat = 1
var alpha:CGFloat = 1
value.getHue(&hue, saturation: &saturation, brightness: &brightness, alpha: &alpha)
a = alpha
if hue != h || pickerImage1 === nil {
self.h = hue
}
currentPoint = CGPoint(x: saturation * bounds.width, y: brightness * bounds.height)
self.setNeedsDisplay()
}
get {
return UIColor(hue: h, saturation: saturationFromCurrentPoint(), brightness: brigthnessFromCurrentPoint(), alpha: a)
}
}
public override init(frame: CGRect) {
super.init(frame: frame)
commonInit()
}
public required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
commonInit()
}
func commonInit() {
isUserInteractionEnabled = true
clipsToBounds = false
self.addObserver(self, forKeyPath: "bounds", options: [NSKeyValueObservingOptions.new, NSKeyValueObservingOptions.initial], context: nil)
}
deinit {
self.removeObserver(self, forKeyPath: "bounds")
}
open override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
if keyPath == "bounds" {
if let pImage1 = pickerImage1 {
pImage1.changeSize(Int(self.bounds.width), height: Int(self.bounds.height))
}
if let pImage2 = pickerImage2 {
pImage2.changeSize(Int(self.bounds.width), height: Int(self.bounds.height))
}
renderBitmap()
self.setNeedsDisplay()
} else {
super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
}
}
open override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
let touch = touches.first! as UITouch
handleTouche(touch, ended: false)
}
open override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
let touch = touches.first! as UITouch
handleTouche(touch, ended: false)
}
open override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
let touch = touches.first! as UITouch
handleTouche(touch, ended: true)
}
fileprivate func handleColorChange(_ color:UIColor, changing:Bool) {
if color !== self.color {
if let handler = onColorChange {
handler(color, !changing)
}
setNeedsDisplay()
}
}
fileprivate func handleTouche(_ touch:UITouch, ended:Bool) {
// set current point
let point = touch.location(in: self)
if self.bounds.contains(point) {
currentPoint = point
} else {
let x:CGFloat = min(bounds.width, max(0, point.x))
let y:CGFloat = min(bounds.width, max(0, point.y))
currentPoint = CGPoint(x: x, y: y)
}
handleColorChange(pointToColor(point), changing: !ended)
}
fileprivate func pointToColor(_ point:CGPoint) ->UIColor {
let s:CGFloat = min(1, max(0, (1.0 / bounds.width) * point.x))
let b:CGFloat = min(1, max(0, (1.0 / bounds.height) * point.y))
return UIColor(hue: h, saturation: s, brightness: b, alpha:a)
}
fileprivate func renderBitmap() {
if self.bounds.isEmpty {
return
}
if !lock.try() {
rerender = true
return
}
rerender = false
if pickerImage1 == nil {
self.pickerImage1 = PickerImage(width: Int(bounds.width), height: Int(bounds.height))
self.pickerImage2 = PickerImage(width: Int(bounds.width), height: Int(bounds.height))
}
opQueue.addOperation { () -> Void in
// Write colors to data array
if self.data1Shown { self.pickerImage2!.writeColorData(self.h, a:self.a) }
else { self.pickerImage1!.writeColorData(self.h, a:self.a)}
// flip images
// self.image = self.data1Shown ? self.pickerImage2!.image! : self.pickerImage1!.image!
self.data1Shown = !self.data1Shown
// make changes visible
OperationQueue.main.addOperation({ () -> Void in
self.setNeedsDisplay()
self.lock.unlock()
if self.rerender {
self.renderBitmap()
}
})
}
}
open override func draw(_ rect: CGRect) {
if let img = image {
img.draw(in: rect)
}
//// Oval Drawing
let ovalPath = UIBezierPath(ovalIn: CGRect(x: currentPoint.x - 5, y: currentPoint.y - 5, width: 10, height: 10))
UIColor.white.setStroke()
ovalPath.lineWidth = 1
ovalPath.stroke()
//// Oval 2 Drawing
let oval2Path = UIBezierPath(ovalIn: CGRect(x: currentPoint.x - 4, y: currentPoint.y - 4, width: 8, height: 8))
UIColor.black.setStroke()
oval2Path.lineWidth = 1
oval2Path.stroke()
}
}

Answer 1

It's not a problem of Swift 4, but a problem of iOS 11. You may find your code works on iOS 10 simulator.
The original code seemingly works in iOS 10, depending on just a luck.
In this part of the code:
init(width:Int, height:Int) {
self.width = width
self.height = height
let size:Int = width * height * 4
mutableData = CFDataCreateMutable(kCFAllocatorDefault, size)
createImageFromData(width, height: height)
}
The property mutableData is initialized with a CFMutableData of capacity: size, and empty (that is, content-less).
And in iOS 11, the initializer CGDataProvider.init(data:) rejects an empty CFData as it should not be empty as a data provider.
A quick fix would be something like this:
init(width:Int, height:Int) {
self.width = width
self.height = height
let size:Int = width * height * 4
mutableData = CFDataCreateMutable(kCFAllocatorDefault, size)
CFDataSetLength(mutableData, size) //<-set the length of the data
createImageFromData(width, height: height)
}
But I'm not sure other parts of the code would work as expected in iOS 11.

Answer 2

The problem is you added let to that line and it creates a new variable call provider within the function createImageFromData. That way, it's never passed to the provider parameter of the class and then, it's always null. Just remove the let and it should work properly.
fileprivate func createImageFromData(_ width:Int, height:Int) {
let colorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedFirst.rawValue)
provider = CGDataProvider(data: mutableData)
imageSource = CGImageSourceCreateWithDataProvider(provider!, nil)
let cgimg = CGImage(width: Int(width), height: Int(height), bitsPerComponent: Int(8), bitsPerPixel: Int(32), bytesPerRow: Int(width) * Int(4),
space: colorSpace, bitmapInfo: bitmapInfo, provider: provider!, decode: nil, shouldInterpolate: true, intent: CGColorRenderingIntent.defaultIntent)
image = UIImage(cgImage: cgimg!)
}