将 EXIF 数据保存为 JPEG - Swift

Question

我目前正在尝试使用 UIImagePickerController 在应用程序中拍摄照片，将它们保存到本地数据库并稍后将它们上传到服务。

但元数据（尤其是 EXIF）似乎并未自动与该图像捆绑在一起。我尝试像这样提取它：

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any])
{ 
    self.imageDelegate?.saveImage( image: info[UIImagePickerControllerOriginalImage] as! UIImage, metadata: (info[UIImagePickerControllerMediaMetadata] as? NSDictionary)! ) 
    // ...
}

现在我应该拥有图像和元数据，但如何将其存储到 JPEG 文件中？我需要服务器上图像中的 GPS 数据。

我目前正在直接从相机胶卷中的 UImage 创建图像：

UIImageJPEGRepresentation(image,CGFloat(Constants.JPEG_QUALITY))

这将被存储并上传。

我读过可能有使用“CGImageDestination”的可能性，但我不知道如何在我的情况下使用它们。

Answer 1

我的解决方案：

func toJpegWithExif(image: UIImage, metadata: NSDictionary, location: CLLocation?) -> Data? {
    return autoreleasepool(invoking: { () -> Data in
        let data = NSMutableData()
        let options = metadata.mutableCopy() as! NSMutableDictionary
        options[ kCGImageDestinationLossyCompressionQuality ] = CGFloat(Constants.JPEG_QUALITY)

        // if location is available, add GPS data, thanks to https://gist.github.com/nitrag/343fe13f01bb0ef3692f2ae2dfe33e86
        if ( nil != location ) {
            let gpsData = NSMutableDictionary()

            let altitudeRef = Int(location!.altitude < 0.0 ? 1 : 0)
            let latitudeRef = location!.coordinate.latitude < 0.0 ? "S" : "N"
            let longitudeRef = location!.coordinate.longitude < 0.0 ? "W" : "E"

            // GPS metadata
            gpsData[(kCGImagePropertyGPSLatitude as String)] = abs(location!.coordinate.latitude)
            gpsData[(kCGImagePropertyGPSLongitude as String)] = abs(location!.coordinate.longitude)
            gpsData[(kCGImagePropertyGPSLatitudeRef as String)] = latitudeRef
            gpsData[(kCGImagePropertyGPSLongitudeRef as String)] = longitudeRef
            gpsData[(kCGImagePropertyGPSAltitude as String)] = Int(abs(location!.altitude))
            gpsData[(kCGImagePropertyGPSAltitudeRef as String)] = altitudeRef
            gpsData[(kCGImagePropertyGPSTimeStamp as String)] = location!.timestamp.isoTime()
            gpsData[(kCGImagePropertyGPSDateStamp as String)] = location!.timestamp.isoDate()
            gpsData[(kCGImagePropertyGPSVersion as String)] = "2.2.0.0"

            options[ kCGImagePropertyGPSDictionary as String ] = gpsData
        }

        let imageDestinationRef = CGImageDestinationCreateWithData(data as CFMutableData, kUTTypeJPEG, 1, nil)!
        CGImageDestinationAddImage(imageDestinationRef, image.cgImage!, options)
        CGImageDestinationFinalize(imageDestinationRef)
        return data as Data
    })
}

extension Date {

    func isoDate() -> String {
        let f = DateFormatter()
        f.timeZone = TimeZone(abbreviation: "UTC")
        f.dateFormat = "yyyy:MM:dd"
        return f.string(from: self)
    }

    func isoTime() -> String {
        let f = DateFormatter()
        f.timeZone = TimeZone(abbreviation: "UTC")
        f.dateFormat = "HH:mm:ss.SSSSSS"
        return f.string(from: self)
    }
}

该方法将 UIImage 转换为 Jpeg，其中包含来自相机的 EXIF 数据以及来自 CLLocationManager 的可选 GPS 位置。