RRLazyJunCore.swift

typealias Filter = CIImage -> CIImage

struct RRLazyJunCore {
    let filter: Filter
    
    init(filter: Filter = { $0 }) { // 这个就比较尴尬了
        self.filter = filter
    }
}

extension RRLazyJunCore {
    func blur(radius: Double) -> RRLazyJunCore {
        return self >>> RRLazyJunCore { image in
            let parameters = [
                kCIInputRadiusKey: radius,
                kCIInputImageKey: image
            ]
            guard let filter = CIFilter(name: "CIGaussianBlur", withInputParameters: parameters) else { fatalError() }
            guard let outputImage = filter.outputImage else { fatalError() }
            return outputImage
        }
    }
    
    func cropped(rect: CGRect) -> RRLazyJunCore {
        return self >>> RRLazyJunCore { $0.imageByCroppingToRect(rect) }
    }
    
    func scale(scale: Double) -> RRLazyJunCore {
        return self >>> RRLazyJunCore { image in
            let parameters = [
                kCIInputImageKey: image,
                kCIInputScaleKey: scale,
                kCIInputAspectRatioKey: 1
            ]
            guard let filter = CIFilter(name: "CILanczosScaleTransform", withInputParameters: parameters) else { fatalError() }
            guard let outputImage = filter.outputImage else { fatalError() }
            return outputImage
        }
    }
}

func >>> (lhs: RRLazyJunCore, rhs: RRLazyJunCore) -> RRLazyJunCore {
    return RRLazyJunCore { image in
        lhs.filter(rhs.filter(image))
    }
}

//RRLazyJunCore()
//    .blur(blurRadius)
//    .cropped(CGRect(x: 0, y: 0, width: 20, height: 20))
//    .scale(3)
//    .filter(image)