/*

    Copyright (C) 2016 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

                PhotoFilter has a class function for returning a filtered image.

*/

import UIKit

class PhotoFilter {

    /// This supports implicit progress composition.

    class func filteredImage(_ image: UIImage) -> UIImage? {

        /*

            Set up the progress. First thing! It's indeterminate since we don't

            have any information about how long this is going to take.

            `NSProgress(totalUnitCount:)` convenience adds itself as a child to the currentProgress.

        */

        let progress = Progress(totalUnitCount: -1)

        progress.isCancellable = false

        progress.isPausable = false

        var outputImage: UIImage?

        if let filter = CIFilter(name: "CIPhotoEffectTransfer"), let cgImage = image.cgImage {

            let filterInput = CIImage(cgImage: cgImage)

            filter.setValue(filterInput, forKey: "inputImage")

            guard let filterOutput = filter.outputImage else { return outputImage }

            let context = CIContext(options: [:])

            let outputCGImage = context.createCGImage(filterOutput, from: filterOutput.extent)

            outputImage = UIImage(cgImage: outputCGImage!)

        }

        // We have finished.

        progress.completedUnitCount = 1

        progress.totalUnitCount = 1

        return outputImage

    }

}