【Swift CIFilter】CIHighlightShadowAdjustでハイライトを補正する方法を解説

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var imageView: UIImageView!
    @IBOutlet weak var valueSlider: UISlider!
    @IBOutlet weak var valueLabel: UILabel!

    private var ciFilter: CIFilter!

    override func viewDidLoad() {
        super.viewDidLoad()

        title = "ハイライト"

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

        imageView.image = uiImage

        // Filterに合わせた最大値、最小値、初期値の設定
        valueSlider.maximumValue = 1
        valueSlider.minimumValue = 0
        valueSlider.value = 1

        valueLabel.text = String(valueSlider.value)

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

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

    @IBAction func valueChanged(_ sender: UISlider) {
        valueLabel.text = String(sender.value)

        // ハイライトの設定
        ciFilter.setValue(sender.value, forKey: "inputHighlightAmount")

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