Hi. Nghia posted a nice article about color lookup tables with Core Image. Now I want to port that code to SWIFT, but all I get is a pink screen :D Actually just need the method of the CIFilter-category. As far as I can see the problem is the converting the data to an NSData object. The post can be found here http://nghiatran.me/2014/06/filter-m…

gistfile1.swift

import Foundation
import GLKit

class ResponseFilter : CIFilter {
    var inputImage:CIImage?
    var responseName: NSString {
        get {
            return responseName_
        }
        set(newName) {
            responseName_ = newName
            loadCubeDataWithName(name: responseName_)
        }
    }
    
    private var nsdata_:AnyObject?
    private var responseName_: String = ""
    
    override init() {
        super.init()
        nsdata_ = nil
    }
    
    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    
    override var outputImage: CIImage! {
        get {
            if nsdata_ == nil {
                return inputImage
            }
            var filter = CIFilter(name: "CIColorCube")
            filter.setValue(nsdata_, forKey: "inputCubeData")
            filter.setValue(64, forKey: "inputCubeDimension")
            filter.setValue(inputImage, forKey: kCIInputImageKey)
            return filter.outputImage
        }
    }
    
    func loadCubeDataWithName(#name:String) {
        var n:UInt = 64
        var image = UIImage(named: name)
        var width = CGImageGetWidth(image!.CGImage)
        var height = CGImageGetHeight(image!.CGImage)
        var rowNum = height / n
        var columnNum = width / n
        if width % n != 0 || height % n != 0 || rowNum * columnNum != n {
            println("Damn invalid LUT image")
            nsdata_ = nil
            return
        }
        
        var bitmap:[CUnsignedChar] = self.createRGBABitmapFromImage(image!.CGImage)
        let size:Int = Int(n * n * n * 4)
        var data = [CFloat](count:size, repeatedValue: 0)
        var bitmapOffset:Int = 0
        var z:UInt = 0
        var callTime = 0
        for (var row:UInt = 0; row < rowNum; row++){
            println("Row \(row)")
            for (var y:UInt = 0; y < n; y++){
                var tmp = z
                for (var col:UInt = 0; col < columnNum; col++) {
                    for (var x:UInt = 0; x < n; x++){
                        var r = CFloat(bitmap[bitmapOffset])
                        var g = CFloat(bitmap[bitmapOffset + 1])
                        var b = CFloat(bitmap[bitmapOffset + 2])
                        var a = CFloat(bitmap[bitmapOffset + 3])
                        var dataOffset = Int((z*n*n + y*n + x) * 4)
                        data[dataOffset] = r / 255.0
                        data[dataOffset + 1] = g / 255.0
                        data[dataOffset + 2] = b / 255.0
                        data[dataOffset + 3] = a / 255.0
                        bitmapOffset += 4
                        callTime++
                    }
                    z++
                }
                z = tmp
            }
            z += columnNum
        }

        nsdata_ = NSData(bytesNoCopy: &data, length: size, freeWhenDone: true)
    
    }
    
    func createRGBABitmapFromImage(image:CGImageRef) -> [CUnsignedChar] {
        var bitmapSize:Int
        var bytesPerRow:UInt
        var width = CGImageGetWidth(image)
        var height = CGImageGetHeight(image)
        bytesPerRow = width * 4
        bitmapSize  = Int(bytesPerRow * height)
        var bitmap = [CUnsignedChar](count:bitmapSize, repeatedValue: 0)
        let colorSpace:CGColorSpace = CGColorSpaceCreateDeviceRGB()
        let bitmapInfo = CGBitmapInfo(CGImageAlphaInfo.PremultipliedLast.rawValue)
        let context = CGBitmapContextCreate(&bitmap, width, height, 8, bytesPerRow, colorSpace, bitmapInfo)
        CGContextDrawImage(context, CGRectMake(0, 0, CGFloat(width), CGFloat(height)), image)
        return bitmap
    }
}