如果您需要以正确的旋转方式保存 PNG，如果它的方向不是 .up，则需要重新绘制图像.您可以按如下方式重绘它:

If you need to save your PNG with correct rotation you will need to redraw your image if its orientation it is not .up. You can redraw it as follow:

extension UIImage {
    func png(isOpaque: Bool = true) -> Data? { flattened(isOpaque: isOpaque)?.pngData() }
    func flattened(isOpaque: Bool = true) -> UIImage? {
        if imageOrientation == .up { return self }
        UIGraphicsBeginImageContextWithOptions(size, isOpaque, scale)
        defer { UIGraphicsEndImageContext() }
        draw(in: CGRect(origin: .zero, size: size))
        return UIGraphicsGetImageFromCurrentImageContext()
    }
}

编辑/更新:

对于 iOS10+ tvOS10+ 你可以使用 UIGraphicsImageRenderer:

For iOS10+ tvOS10+ you can use UIGraphicsImageRenderer:

extension UIImage {
    func png(isOpaque: Bool = true) -> Data? { flattened(isOpaque: isOpaque).pngData() }
    func flattened(isOpaque: Bool = true) -> UIImage {
        if imageOrientation == .up { return self }
        let format = imageRendererFormat
        format.opaque = isOpaque
        return UIGraphicsImageRenderer(size: size, format: format).image { _ in draw(at: .zero) }
    }
}

游乐场测试:

Playground testing:

用于不透明的图像:

let image = UIImage(data: try! Data(contentsOf: URL(string: "https://i.stack.imgur.com/varL9.jpg")!))!

if let data = image.png() {
    let imageFromPNGData = UIImage(data: data)
}

具有透明度:

With transparency :

if let data = image.png(isOpaque: false) {
    let imageFromPNGData = UIImage(data: data)
}