Swift PNG 图像以不正确的方向保存

Question

如果我在保存之前使用图像，这是正常的。但如果我保存它并稍后使用它，它就会旋转 90 度。我怎样才能确保它不会横向保存？

func saveEvent(_ center1: CLLocation, title2: String, imagePicked1: UIImage)
    {
        let data = UIImagePNGRepresentation(imagePicked1);///
        let url = NSURL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(NSUUID().uuidString+".dat")
        do {
            try data!.write(to: url!, options: [])
        } catch let e as NSError {
            print("Error! \(e)");
            return
        }
        let image11 = CKAsset(fileURL: url!)

        self.eventRecord.setObject(image11 as CKAsset, forKey: "Picture")
        let publicData = CKContainer.default().publicCloudDatabase
            publicData.save(self.eventRecord, completionHandler: { record, error in
                if error == nil
                {
                    print("Image saved")
                }else{
                    print(error!)
                }
        })
    }

Answer 1

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

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+，您可以使用 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) }
    }
}

---

Playground 测试：

不透明图像的用法：

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

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

---

具有透明度：

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

Answer 2

您也可以使用它来防止它改变方向。

func rotateImage(image: UIImage) -> UIImage? {
    if (image.imageOrientation == UIImage.Orientation.up ) {
        return image
    }
    UIGraphicsBeginImageContext(image.size)
    image.draw(in: CGRect(origin: CGPoint.zero, size: image.size))
    let copy = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return copy
}

Answer 3

只需将图像转换为 JPEG 数据即可。无需重绘图像：

let imageData = image.jpegData(compressionQuality: 1.0)