Swift：从 Firebase 加载时从纵向旋转到横向的图像

Question

我的部分 iOS 应用使用 Firebase 存储来存储和加载用户拍摄/上传的图像。 但是，每次我以纵向将图片上传到 Firebase 时，当我稍后从 Firebase 检索它时，它会以横向显示，因此显示不正确。

我读到 Firebase 存储元数据以确定上传图片的正确方向，但它似乎对我不起作用。

任何人都知道如何获取图像上传的方向，而无需在应用程序代码中手动旋转它？

谢谢！

编辑代码：

上传中：

        let imageMetaData = FIRStorageMetadata()
        imageMetaData.contentType = "image/png"

        var imageData = Data()
        imageData = UIImagePNGRepresentation(chosenImage)!

        let currentUserProfilePictureRef = currentUserStorageRef.child("ProfilePicture")

        currentUserProfilePictureRef.put(imageData, metadata: imageMetaData) { (metaData, error) in
            if error == nil {
                let downloadUrl = metaData?.downloadURL()?.absoluteString
                self.currentUserRef.updateChildValues(["profilePictureUrl": downloadUrl!])
                if (chosenImage.size.width.isLess(than: (chosenImage.size.height))) {
                    self.currentUserRef.updateChildValues(["profilePictureOrientation": "portrait"])
                }
                else {
                    self.currentUserRef.updateChildValues(["profilePictureOrientation": "landscape"])
                }


            } 
        }

检索：

self.currentUserStorageRef.child("ProfilePicture").data(withMaxSize: 20*1024*1024, completion: {(data, error) in
                    var profilePicture = UIImage(data:data!)

                    if(profilePicture?.size.width.isLess(than: (profilePicture?.size.height)!))! {
                        if (pictureOrientation == "landscape") {
                            profilePicture = profilePicture?.rotated(by: Measurement(value: -90.0, unit: .degrees))
                        }
                    } else {
                        if (pictureOrientation == "portrait") {
                            profilePicture = profilePicture?.rotated(by: Measurement(value: 90.0, unit: .degrees))
                        }
                    }

                    self.buttonProfilePicture.setImage(profilePicture, for: .normal)
                    self.buttonProfilePicture.imageView?.contentMode = .scaleAspectFill
                })

Answer 1

根据我自己的个人经验（一年前几乎问过同样的问题），我发现当您使用UIImagePNGRepresentation 保存图像时，它实际上并没有存储该特定图像的方向数据。当您遇到方向问题时，您应该使用UIImageJPEGRepresentation。 JPEG 使用指定图像方向的exif 格式，而PNG 显然没有。如果您使用UIImageJPEGRepresentation保存图片，您的问题应该会得到解决

Answer 2

Swift 5 - 更新

这对我有用，只需在上传之前将其应用于您的 UIImage。

extension UIImage {

func fixedOrientation() -> UIImage? {
    guard imageOrientation != UIImage.Orientation.up else {
        // This is default orientation, don't need to do anything
        return self.copy() as? UIImage
    }

    guard let cgImage = self.cgImage else {
        // CGImage is not available
        return nil
    }

    guard let colorSpace = cgImage.colorSpace, let ctx = CGContext(data: nil, width: Int(size.width), height: Int(size.height), bitsPerComponent: cgImage.bitsPerComponent, bytesPerRow: 0, space: colorSpace, bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue) else {
        return nil // Not able to create CGContext
    }

    var transform: CGAffineTransform = CGAffineTransform.identity

    switch imageOrientation {
    case .down, .downMirrored:
        transform = transform.translatedBy(x: size.width, y: size.height)
        transform = transform.rotated(by: CGFloat.pi)
    case .left, .leftMirrored:
        transform = transform.translatedBy(x: size.width, y: 0)
        transform = transform.rotated(by: CGFloat.pi / 2.0)
    case .right, .rightMirrored:
        transform = transform.translatedBy(x: 0, y: size.height)
        transform = transform.rotated(by: CGFloat.pi / -2.0)
    case .up, .upMirrored:
        break
    @unknown default:
        break
    }

    // Flip image one more time if needed to, this is to prevent flipped image
    switch imageOrientation {
    case .upMirrored, .downMirrored:
        transform = transform.translatedBy(x: size.width, y: 0)
        transform = transform.scaledBy(x: -1, y: 1)
    case .leftMirrored, .rightMirrored:
        transform = transform.translatedBy(x: size.height, y: 0)
        transform = transform.scaledBy(x: -1, y: 1)
    case .up, .down, .left, .right:
        break
    @unknown default:
        break
    }

    ctx.concatenate(transform)

    switch imageOrientation {
    case .left, .leftMirrored, .right, .rightMirrored:
        ctx.draw(cgImage, in: CGRect(x: 0, y: 0, width: size.height, height: size.width))
    default:
        ctx.draw(cgImage, in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
        break
    }

    guard let newCGImage = ctx.makeImage() else { return nil }
    return UIImage.init(cgImage: newCGImage, scale: 1, orientation: .up)
}

}

Answer 3

只是一个更新，最近版本的 xcode 中 UIImageJPEGRepresentation 已更改为 jpegData。

jpegData(compressionQuality: 1.0) 1.0 表示高质量，0 表示低质量。