UIImageView+contentClippingRect.swift

extension UIImageView {
    var contentClippingRect: CGRect {
        guard let image = image else { return bounds }
        guard contentMode == .scaleAspectFit else { return bounds }
        guard image.size.width > 0, image.size.height > 0 else { return bounds }

        let scale: CGFloat
        let scaleByWidth = bounds.width / image.size.width
        let scalebyHeight = bounds.height / image.size.height

        // attempt to scale by width, and see if the height exceeds the bounds
        if image.size.height * scaleByWidth < bounds.height {
            // we're within the bounds, so it's the right scale
            scale = scaleByWidth
        } else {
            // the image exceeded the bounds, so scale by the height ratio instead
            scale = scalebyHeight
        }

        let size = CGSize(width: image.size.width * scale, height: image.size.height * scale)
        let x = (bounds.width - size.width) / 2.0
        let y = (bounds.height - size.height) / 2.0

        return CGRect(x: x, y: y, width: size.width, height: size.height)
    }
}