Question

我试图在Swift中编写一个iOS应用程序，让用户拍照，然后我会将一些额外的数据叠加到图像上。我希望图像包含位置数据。我正在使用AVCapturePhoto，我可以在文档中看到它有一些元数据变量，但我找不到有关如何使用它们的任何信息。当我现在使用我的应用拍摄照片时，它在EXIF信息中没有位置数据。

如何设置捕获会话以嵌入位置数据？

Answer 1

我还没有处理新的IOS 11 AVCapturePhoto对象，因此这个答案必须对如何访问数据做出一些假设，但理论上所有这些都应该有效。

在添加位置数据之前，您需要询问用户是否可以使用他们的位置。在您的Info.plist中添加“隐私 - 使用中的位置”标签。然后在初始化的某处添加以下代码。

// Request authorization for location manager 
switch CLLocationManager.authorizationStatus() {
case .authorizedWhenInUse:
    break

case .notDetermined:
    locationManager.requestWhenInUseAuthorization()
    locationManagerStatus = CLLocationManager.authorizationStatus()

default:
    locationManagerStatus = .denied
}

现在，以下内容将创建一个包含位置信息的字典。

// create GPS metadata properties
func createLocationMetadata() -> NSMutableDictionary? {

    guard CLLocationManager.authorizationStatus() == .authorizedWhenInUse else {return nil}

    if let location = locationManager.location {
        let gpsDictionary = NSMutableDictionary()
        var latitude = location.coordinate.latitude
        var longitude = location.coordinate.longitude
        var altitude = location.altitude
        var latitudeRef = "N"
        var longitudeRef = "E"
        var altitudeRef = 0

        if latitude < 0.0 {
            latitude = -latitude
            latitudeRef = "S"
        }

        if longitude < 0.0 {
            longitude = -longitude
            longitudeRef = "W"
        }

        if altitude < 0.0 {
            altitude = -altitude
            altitudeRef = 1
        }

        let formatter = DateFormatter()
        formatter.dateFormat = "yyyy:MM:dd"
        gpsDictionary[kCGImagePropertyGPSDateStamp] = formatter.string(from:location.timestamp)
        formatter.dateFormat = "HH:mm:ss"
        gpsDictionary[kCGImagePropertyGPSTimeStamp] = formatter.string(from:location.timestamp)
        gpsDictionary[kCGImagePropertyGPSLatitudeRef] = latitudeRef
        gpsDictionary[kCGImagePropertyGPSLatitude] = latitude
        gpsDictionary[kCGImagePropertyGPSLongitudeRef] = longitudeRef
        gpsDictionary[kCGImagePropertyGPSLongitude] = longitude
        gpsDictionary[kCGImagePropertyGPSDOP] = location.horizontalAccuracy
        gpsDictionary[kCGImagePropertyGPSAltitudeRef] = altitudeRef
        gpsDictionary[kCGImagePropertyGPSAltitude] = altitude

        if let heading = locationManager.heading {
            gpsDictionary[kCGImagePropertyGPSImgDirectionRef] = "T"
            gpsDictionary[kCGImagePropertyGPSImgDirection] = heading.trueHeading
        }

        return gpsDictionary;
    }
    return nil
}

这是我必须做一些猜测的地方，因为我没有处理过IOS 11 AVPhotoCapture。您将需要图像数据的文件数据表示。我假设

AVCapturePhoto.fileDataRepresentation()

返回此信息。您还需要原始文件元数据。我猜猜想

AVCapturePhoto.metadata

包含这个。通过这些假设，以下函数将为您提供包含其他位置数据的文件数据表示。可能有更新的IOS 11方法以更清洁的方式执行此操作。

func getFileRepresentationWithLocationData(photo : AVCapturePhoto) -> Data {
    // get image metadata
    var properties = photo.metadata

    // add gps data to metadata
    if let gpsDictionary = createLocationMetadata() {
        properties[kCGImagePropertyGPSDictionary as String] = gpsDictionary
    }

    // create new file representation with edited metadata
    return photo.fileDataRepresentation(withReplacementMetadata:properties,
        replacementEmbeddedThumbnailPhotoFormat:photo.embeddedThumbnailPhotoFormat,
        replacementEmbeddedThumbnailPixelBuffer:photo.previewPixelBuffer,
        replacementDepthData:photo.depthData)
}

Answer 2

@adamfowlerphoto到目前为止，我在这个问题上能找到最好的答案！

AVCapturePhoto.fileDataRepresentation(withReplacementMetadata:replacementEmbeddedThumbnailPhotoFormat:replacementEmbeddedThumbnailPixelBuffer:replacementDepthData:) 在iOS 12中已弃用。对于新API，您必须使用方法AVCapturePhotoFileDataRepresentationCustomizer实现replacementMetadata()协议。这是更新的代码：

extension CameraViewController: AVCapturePhotoFileDataRepresentationCustomizer {

    // create GPS metadata properties
    func createLocationMetadata() -> NSMutableDictionary? {
        if let location = locationManager.location {
            let gpsDictionary = NSMutableDictionary()
            var latitude = location.coordinate.latitude
            var longitude = location.coordinate.longitude
            var altitude = location.altitude
            var latitudeRef = "N"
            var longitudeRef = "E"
            var altitudeRef = 0

            if latitude < 0.0 {
                latitude = -latitude
                latitudeRef = "S"
            }

            if longitude < 0.0 {
                longitude = -longitude
                longitudeRef = "W"
            }

            if altitude < 0.0 {
                altitude = -altitude
                altitudeRef = 1
            }

            let formatter = DateFormatter()
            formatter.dateFormat = "yyyy:MM:dd"
            gpsDictionary[kCGImagePropertyGPSDateStamp] = formatter.string(from:location.timestamp)
            formatter.dateFormat = "HH:mm:ss"
            gpsDictionary[kCGImagePropertyGPSTimeStamp] = formatter.string(from:location.timestamp)
            gpsDictionary[kCGImagePropertyGPSLatitudeRef] = latitudeRef
            gpsDictionary[kCGImagePropertyGPSLatitude] = latitude
            gpsDictionary[kCGImagePropertyGPSLongitudeRef] = longitudeRef
            gpsDictionary[kCGImagePropertyGPSLongitude] = longitude
            gpsDictionary[kCGImagePropertyGPSDOP] = location.horizontalAccuracy
            gpsDictionary[kCGImagePropertyGPSAltitudeRef] = altitudeRef
            gpsDictionary[kCGImagePropertyGPSAltitude] = altitude

            if let heading = locationManager.heading {
                gpsDictionary[kCGImagePropertyGPSImgDirectionRef] = "T"
                gpsDictionary[kCGImagePropertyGPSImgDirection] = heading.trueHeading
            }

            return gpsDictionary;
        }
        return nil
    }
    
    func getFileRepresentationWithLocationData(photo : AVCapturePhoto) -> Data {
        // get image metadata
        var properties = photo.metadata

        // add gps data to metadata
        if let gpsDictionary = createLocationMetadata() {
            properties[kCGImagePropertyGPSDictionary as String] = gpsDictionary
        }

        // create new file representation with edited metadata
        
        return photo.fileDataRepresentation(with: self) ?? Data()
    }
    
    func replacementMetadata(for photo: AVCapturePhoto) -> [String : Any]? {
        var properties = photo.metadata

        // add gps data to metadata
        if let gpsDictionary = createLocationMetadata() {
            properties[kCGImagePropertyGPSDictionary as String] = gpsDictionary
        }
        return properties
    }
}

要打印结果，可以使用以下方法：

    static func printEXIFData(imageData: Data) {
        var exifData: CFDictionary? = nil
        imageData.withUnsafeBytes {
            let bytes = $0.baseAddress?.assumingMemoryBound(to: UInt8.self)
            if let cfData = CFDataCreate(kCFAllocatorDefault, bytes, imageData.count),
               let source = CGImageSourceCreateWithData(cfData, nil) {
                exifData = CGImageSourceCopyPropertiesAtIndex(source, 0, nil)
                print(exifData)
            }
        }
    }

请勿尝试将imageData转换为JPEG表示形式，因为它将丢弃GPS元数据。（来源：https://stackoverflow.com/a/10339278/647644）

let data = jpegData(compressionQuality: 1.0) // NOOOOO

如何使用AVCapturePhoto包含位置数据？

2 个答案: