尝试从UIImagePickerController中提取GPS元数据，但NSLog显示为空 [英] Trying to Pull GPS Metadata from UIImagePickerController but NSLog Shows Null

问题描述

使用UIImagePickerController我试图从图像的元数据中收集GPS信息。这里是我的代码示例：

  NSDictionary * imageMetadata = [info objectForKey：UIImagePickerControllerMediaMetadata]; 
 NSLog（@Working META：％@，imageMetadata）; 
 
 CGDataProviderRef dataProvider = CGImageGetDataProvider（originalImage.CGImage）; 
 CFDataRef data = CGDataProviderCopyData（dataProvider）; 
 CGImageSourceRef imageSource = CGImageSourceCreateWithData（data，nil）; 
 NSDictionary * metaDict =（__bridge NSDictionary *）（CGImageSourceCopyProperties（imageSource，nil））; 
 NSLog（@不存在META：％@，metaDict）; 
  

在NSLog的输出中，我可以看到Working Meta包含所有关联的内容。不幸的是，不工作元输出空。从我可以告诉我需要增强图像源和CFDictionary上的选项，而不是使用零。我在正确的道路上吗？如果是这样，我应该怎样改变GPS数据？ 试试获取源EXIF字典的可变副本像这样：

$ b

  UIImage * image = [info objectForKey：UIImagePickerControllerOriginalImage]; 
 NSData * jpeg = UIImageJPEGRepresentation（image，image.scale）; 
 CGImageSourceRef source = CGImageSourceCreateWithData（（__ bridge CFDataRef）jpeg，NULL）; 
 NSDictionary * metadata =（__bridge NSDictionary *）CGImageSourceCopyPropertiesAtIndex（source，0，NULL）; 
 NSMutableDictionary * mutableMetadata = [元数据mutableCopy]; 
  

现在将GPS数据设置为该EXIF字典（代码礼貌 GusUtils ）：

  [mutableMetadata setLocation：self.currentLocation] 
  

最后，您需要将这些数据填充到某个目标

  CFStringRef UTI = CGImageSourceGetType（source）; 
 NSMutableData * data = [NSMutableData data]; 
 CGImageDestinationRef destination = CGImageDestinationCreateWithData（（__ bridge CFMutableDataRef）data，UTI，1，NULL）; 
 CGImageDestinationAddImageFromSource（destination，source，0，（__bridge CFDictionaryRef）mutableMetadata）; 
 BOOL success = CGImageDestinationFinalize（destination）; 
  

此时变量 data 应该包含所有信息（图像+ GPS元数据+其他元数据），您可以使用此数据来存储您喜欢的任何地方。

编辑：

要在您的类中添加核心位置功能，请在
标头中声明CLLocationManagerDelegate协议。在 viewDidLoad 中实例化位置管理器： CLLocationManager new];
self.locManager.delegate = self;
self.locManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
self.locManager.distanceFilter = 5.0f; //如果移动5位，位置将被更新
[self.locManager startUpdatingLocation];

并执行以下方法收集位置信息：

   - （void）locationManager：（CLLocationManager *）manager didUpdateLocations：（NSArray *）locations {
 if（！locations || [locations count] == 0）{ 
 return; 
} 
 
 CLLocation * loc = locations [[locations count]  -  1]; 
 if（loc.horizo​​ntalAccuracy <0）{
 return; 
} 
 self.currentLocation = loc; （CLLocation *）newLocation fromLocation：（CLLocation *）oldLocation {
 if（newLocation.horizo​​ntalAccuracy <0）{
} 
  - （void）locationManager：（CLLocationManager *）manager didUpdateToLocation： b $ b回报; 
} 
 self.currentLocation = newLocation; 
} 
  - （void）locationManager：（CLLocationManager *）manager didFailWithError：（NSError *）error {
 NSLog（@core location error：％@，[errors localizedDescription]）; 
 if（[error code]！= kCLErrorLocationUnknown）{
 NSLog（@location service will terminate now）; 
 self.locManager.delegate = nil; 
 [self.locManager stopUpdatingLocation]; 
 
 self.currentLocation = nil; 
 
 
 $ / code> 

另外请确保在离开VC之前停止服务

  self.locManager.delegate = nil; 
 [self.locManager stopUpdatingLocation]; 
  

然后您可以使用 self.currentLocation 你的位置变量。



EDIT2

好像你已经使用GusUtils的NSMutableDictionary + ImageMetadata.h类别。所以我对我的答案做了一些修改。请尝试一下。

Using UIImagePickerController I am attempting to gather GPS info from the metadata of the image. Here is my code sample:

  NSDictionary *imageMetadata = [info objectForKey: UIImagePickerControllerMediaMetadata];
    NSLog(@"Working META: %@",imageMetadata);

    CGDataProviderRef dataProvider = CGImageGetDataProvider(originalImage.CGImage);
    CFDataRef data = CGDataProviderCopyData(dataProvider);
    CGImageSourceRef imageSource = CGImageSourceCreateWithData(data, nil);
    NSDictionary *metaDict = (__bridge NSDictionary *)(CGImageSourceCopyProperties(imageSource, nil));
    NSLog(@"Not WOrking META: %@",metaDict);

In the output from NSLog I can see that Working Meta has all associated content. Unfortunately the Not Working Meta is outputting null. From what I can tell I need to enhance the options on the image source and CFDictionary rather than using nil. Am I on the right path? If so, what change should I make to pull the GPS data through?

解决方案

Try obtaining your mutable copy of the source EXIF dictionary like this:

UIImage *image =  [info objectForKey:UIImagePickerControllerOriginalImage];
NSData *jpeg = UIImageJPEGRepresentation(image,image.scale);
CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)jpeg, NULL);
NSDictionary *metadata = (__bridge NSDictionary *)CGImageSourceCopyPropertiesAtIndex(source,0,NULL);
NSMutableDictionary *mutableMetadata = [metadata mutableCopy];

Now set GPS data to that EXIF dictionary (code courtesy GusUtils):

[mutableMetadata setLocation:self.currentLocation]

And finally you need to populate this data to some destination

CFStringRef UTI = CGImageSourceGetType(source);
NSMutableData *data = [NSMutableData data];
CGImageDestinationRef destination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef) data, UTI, 1, NULL);
CGImageDestinationAddImageFromSource(destination,source, 0, (__bridge CFDictionaryRef) mutableMetadata);
BOOL success = CGImageDestinationFinalize(destination);

At this point the variable data should contain all information(image+GPS metadata+other metadata) and you can use this data to store wherever you like.

EDIT:

To add core location functionality in your class declare CLLocationManagerDelegate protocol in the header. Instantiate a location manager in your viewDidLoad:

self.locManager = [CLLocationManager new];
self.locManager.delegate = self;
self.locManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
self.locManager.distanceFilter = 5.0f; //location would be updated if moved by 5 miter
[self.locManager startUpdatingLocation];

And implement following methods to gather location info:

-(void)locationManager:(CLLocationManager*)manager didUpdateLocations:(NSArray*)locations    {
if (!locations || [locations count] == 0) {
    return;
}

CLLocation* loc = locations[[locations count] - 1];
if (loc.horizontalAccuracy < 0) {
    return;
}
self.currentLocation = loc;
}
-(void)locationManager:(CLLocationManager*)manager didUpdateToLocation:(CLLocation*)newLocation fromLocation:(CLLocation*)oldLocation {
if (newLocation.horizontalAccuracy < 0) {
    return;
}
self.currentLocation = newLocation;
}
-(void)locationManager:(CLLocationManager*)manager didFailWithError:(NSError*)error {
NSLog(@"core location error: %@",[error localizedDescription]);
if ([error code] != kCLErrorLocationUnknown) {
    NSLog(@"location service will terminate now");
    self.locManager.delegate = nil;
    [self.locManager stopUpdatingLocation];

    self.currentLocation = nil;
}
}

Also make sure to stop the service before leaving the VC

self.locManager.delegate = nil;
[self.locManager stopUpdatingLocation];

Then you can use self.currentLocation for your `location variable.

EDIT2

Ok its seems that you are already using "NSMutableDictionary+ImageMetadata.h" category from GusUtils. So I have made some modifications to my answer. Please give it a try.

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