Swift: Cannot convert the expression's type

Question

I'm trying to write my own CIFilter in Swift. I'm having problems when it comes to the real beef of the class, which is the outputImage method:

class CustomFilter : CIFilter {
    var kernel: CIKernel

    var inputImage: CIImage
    var color: CIColor
    var threshold: NSNumber

    // ... stuff omitted ...

    func outputImage() -> CIImage {
        let zero = NSNumber(double: 0 as Double)
        let width = NSNumber(double: inputImage.extent().size.width.native as Double)
        let height = NSNumber(double: inputImage.extent().size.height.native as Double)

        let src = CISampler(image: inputImage)
        let arguments  = [src, color, threshold] as [AnyObject]
        let extent = [zero, zero, width, height]

        return self.apply(
            kernel,
            arguments: arguments,
            options: (kCIApplyOptionExtent: extent)
        )
    }
}

The compiler error message concerning the last line of the method is as follows:

Cannot convert the expression's type '(@lvalue CIKernel, arguments: [AnyObject], options: (kCIApplyOptionExtent: [NSNumber]))' to type 'CIKernel!'

Can someone with more Swift or Core Image experience please point me in the right direction? I couldn't find an answer even after an hour of trying and googling...

Answer 1

Use square brackets to create the options dictionary:

return self.apply(kernel, arguments: arguments, options: [kCIApplyOptionExtent: extent])

The required argument is of type [NSObject : AnyObject]!