SWIFT - UIImage(contentsOfFile: "") SLOWER than UIImage(imageLiteralResourceName: "") WHY? - swift

Question

Faced with a strange issue when UIImage(contentsOfFile: "") SLOWER than UIImage(imageLiteralResourceName: "")
In my CALayer I have ONE global variable
let img:UIImage? = nil
...and If the viewDidLoad I'm loading img using "contentsOfFile", then it draw this image very SLOW. (For example during touchMove+refresh CPU under 99-100% and FPS 5-10)
img = UIImage(cgImage: UIImage(contentsOfFile: controlPath! + "/line.png")!.cgImage!, scale: 2.0, orientation: UIImage.Orientation.up)
But... if in the viewDidLoad I'm loading the same img using "imageLiteralResourceName" or UIImage(data:NSDATA) - then it works Perfect! CPU load is low, FPS40-60 WHY???
img = UIImage(cgImage: UIImage(imageLiteralResourceName: "line.png").cgImage!, scale: 2.0, orientation: UIImage.Orientation.up).cgImage
Code that draw 100 copies of this image on screen:
override public func draw(in ctx: CGContext) {
...
//here we draw this image... nothing special
for _ in 0...99{
ctx.draw(img.cgImage!, in: randomPositionRect)
}
...
}
refreshing screen:
override public func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
super.touchesMoved(touches, with: event)
....
myLayer.setNeedsDisplay()
}
PS> in objective c it work fast in both cases. Issue only with SWIFT
Full draw code:
var value = self.frame.size.height/2.0 //this value is changing in touchMove
override public func draw(in ctx: CGContext) {
let height:CGFloat = self.frame.size.height-paddingTop!-paddingBottom!
//rotate screen
ctx.translateBy(x: +(frame.size.width / 2), y: +(frame.size.height / 2))
ctx.rotate(by: degreesToRadians(x: 180))
ctx.scaleBy(x: -1.0, y: 1.0)
ctx.translateBy(x: -(frame.size.width / 2), y: -(frame.size.height / 2))
////
ctx.translateBy(x: 0.0, y: 110)
//Define the degrees needed for each plane to create a circle
let degForPlane = Float(360.0 / CGFloat(panelsCount!))
let radius: CGFloat = height / 2.0
//The current angle offset (initially it is 0... it will change through the pan function)
let vv: CGFloat = ((160.0 / frame.size.height) * (self.value)) + 10
var degX: CGFloat = vv
degX -= 90
degX += 360
/////DRAW Carousel ////
let rect = CGRect(x: 0, y: 0 - (originalPanelSize!.height / 2.0), width: originalPanelSize!.width, height: originalPanelSize!.height)
for i in 0...panelsCount!-1 {
//Create the Matrix identity
var t: CATransform3D = CATransform3DIdentity
//Perform rotate on the matrix identity
t = CATransform3DRotate(t, degreesToRadians(x: degX), 1.0, 0.0, 0.0)
//Perform translate on the current transform matrix (identity + rotate)
t = CATransform3DTranslate(t, 0.0, 0.0, radius)
if i > -1 && ((degX >= -180 && degX <= 90) || (degX >= 270 && degX <= 450)) {
let affine = CGAffineTransform(a: t.m11, b: t.m12, c: t.m21, d: t.m22, tx: t.m41, ty: t.m42)
ctx.saveGState()
ctx.concatenate(affine)
ctx.draw(img!, in: rect)
ctx.restoreGState()
}
degX -= CGFloat(degForPlane)
}
}

Answer 1

My current solution for now to use custom extension that load image by NSData:
Create a file UIImage+ext.swift
import Foundation
import UIKit
extension UIImage{
static func fromFile (path:String)->UIImage? {
if let data = NSData(contentsOfFile: path) {
return UIImage(cgImage: UIImage(data: data as Data)!.cgImage!, scale: UIScreen.main.scale, orientation: UIImage.Orientation.up)
}
return nil
}
}
Use:
let img = UIImage.fromFile(path: "MyFoler1/MyFolder2/File.png")