HaishinKit.swift/HaishinKit/Sources/Extension/AVLayerVideoGravity+Extension.swift

import AVFoundation
import Foundation

extension AVLayerVideoGravity {
    func scale(_ display: CGSize, image: CGSize) -> CGAffineTransform {
        switch self {
        case .resize:
            return .init(scaleX: display.width / image.width, y: display.width / image.height)
        case .resizeAspect:
            let scale = min(display.width / image.width, display.height / image.height)
            return .init(scaleX: scale, y: scale)
        case .resizeAspectFill:
            let scale = max(display.width / image.width, display.height / image.height)
            return .init(scaleX: scale, y: scale)
        default:
            return .init(scaleX: 1.0, y: 1.0)
        }
    }

    func region(_ display: CGRect, image: CGRect) -> CGRect {
        switch self {
        case .resize:
            return image
        case .resizeAspect:
            return image
        case .resizeAspectFill:
            let x = abs(display.width - image.width) / 2
            let y = abs(display.height - image.height) / 2
            return .init(origin: .init(x: x, y: y), size: display.size)
        default:
            return image
        }
    }
}