【Swift CIFilter】CIToneCurveでトーンカーブを補正する方法を解説

import UIKit

class ViewController: UIViewController, ToneCurveDelegate {

    @IBOutlet weak var imageView: UIImageView!
    @IBOutlet weak var tableView: UITableView!

    private var ciFilter: CIFilter!

    private let toneCurveTitleList: [String] = [
        "inputPoint0",
        "inputPoint1",
        "inputPoint2",
        "inputPoint3",
        "inputPoint4"
    ]

    public var toneCurveValueList: [Float] = [0.0, 0.25, 0.50, 0.75, 1.0]

    override func viewDidLoad() {
        super.viewDidLoad()

        title = "トーンカーブ"

        guard let uiImage = UIImage(named: "sample"), let ciImage = uiImage.ciImage ?? CIImage(image: uiImage) else { return }

        imageView.image = uiImage

        // CIFilterの生成
        ciFilter = CIFilter(name: "CIToneCurve")

        // 入力画像の設定
        ciFilter.setValue(ciImage, forKey: kCIInputImageKey)
    }

    func valueSliderChanged(tag: Int, value: Float) {
        toneCurveValueList[tag] = value

        // トーンカーブの設定
        ciFilter.setValue(CIVector(x: 0.0,  y: CGFloat(toneCurveValueList[0])), forKey: "inputPoint0")
        ciFilter.setValue(CIVector(x: 0.25, y: CGFloat(toneCurveValueList[1])), forKey: "inputPoint1")
        ciFilter.setValue(CIVector(x: 0.5,  y: CGFloat(toneCurveValueList[2])), forKey: "inputPoint2")
        ciFilter.setValue(CIVector(x: 0.75, y: CGFloat(toneCurveValueList[3])), forKey: "inputPoint3")
        ciFilter.setValue(CIVector(x: 1.0,  y: CGFloat(toneCurveValueList[4])), forKey: "inputPoint4")

        // Filter適応後の画像を表示
        if let filteredImage = ciFilter.outputImage {
            imageView.image = UIImage(ciImage: filteredImage)
        }
    }
}

extension ViewController: UITableViewDelegate, UITableViewDataSource {

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return toneCurveTitleList.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        guard let cell = tableView.dequeueReusableCell(withIdentifier: "ToneCurveTableViewCell") as? ToneCurveTableViewCell else {
            return UITableViewCell()
        }

        cell.delegate = self
        cell.valueSlider.tag = indexPath.row
        cell.titleLabel.text = toneCurveTitleList[indexPath.row]
        cell.valueSlider.value = toneCurveValueList[indexPath.row]
        cell.valueLabel.text = String(round(cell.valueSlider.value * 100) / 100)

        return cell
    }

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        tableView.deselectRow(at: indexPath, animated: true)
    }
}



protocol ToneCurveDelegate: class {
    func valueSliderChanged(tag: Int, value: Float)
}

class ToneCurveTableViewCell: UITableViewCell {

    @IBOutlet weak var titleLabel: UILabel!
    @IBOutlet weak var valueSlider: UISlider!
    @IBOutlet weak var valueLabel: UILabel!

    public weak var delegate: ToneCurveDelegate?

    override func awakeFromNib() {
        super.awakeFromNib()
    }

    @IBAction func valueChanged(_ sender: UISlider) {
        valueLabel.text = String(round(sender.value * 100) / 100)
        delegate?.valueSliderChanged(tag: sender.tag, value: sender.value)
    }
}