ciblendwithmask.swift

func maskInputImage(){
        
        let bgImage = UIImage.imageFromColor(color: .blue, size: self.inputImage.size, scale: self.inputImage.scale)!

        let beginImage = CIImage(cgImage: inputImage.cgImage!)
        let background = CIImage(cgImage: bgImage.cgImage!)
        let mask = CIImage(cgImage: self.outputImage.cgImage!)
        
        if let compositeImage = CIFilter(name: "CIBlendWithMask", parameters: [
                                        kCIInputImageKey: beginImage,
                                        kCIInputBackgroundImageKey:background,
                                        kCIInputMaskImageKey:mask])?.outputImage
        {
            
            let ciContext = CIContext(options: nil)
            let filteredImageRef = ciContext.createCGImage(compositeImage, from: compositeImage.extent)
            
            self.outputImage = UIImage(cgImage: filteredImageRef!)
        }
    }