iOS 拍照中加入GPS和具体地理位置

最近有一个需求，要求用手机拍个照片，并切需要拍摄时间，拍摄gps，拍摄具体街道信息。

首先要感谢PhotoGPSdemo的作者，你可以到这里下载demo http://www.cocoachina.com/bbs/read.php?tid=130501。

以前，总认为jpg就是包含了像素信息的2进制文件，其实，jpg中还可以包含许多起它的信息，只不过我们平常用查看jpg属性时，系统没有给我们把信息全部显示出来而已！

在iOS中，提供了一组函数来操作jpg的这些额外的信息，你需要#import <ImageIO/ImageIO.h>才能使用他们。

首先，需要注意的是，UIImage对象中是没有这些信息的，它仅仅包含图像本身，jpg才包含这些信息，请不要弄混。

先看看怎么从jpg图片中取得各种额外信息，代码如下

- (IBAction)test
{
    NSString * home = NSHomeDirectory();
    NSData *data = [NSData dataWithContentsOfFile:[NSString stringWithFormat:@"%@/Documents/xx.jpg",home]];

    CGImageSourceRef imgSource = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);

    CFDictionaryRef metaDataDicRef = CGImageSourceCopyPropertiesAtIndex(imgSource,,nil);
    NSLog(@"cfdictionary %@",(__bridge NSDictionary *)metaDataDicRef);

    NSDictionary *dic = (__bridge NSDictionary *)metaDataDicRef;

    NSDictionary *exifDic = [dic objectForKey:(NSString *)kCGImagePropertyExifDictionary];

    NSString *location = [exifDic objectForKey:(NSString *)kCGImagePropertyExifCameraOwnerName];
    NSLog(@"location is %@",location);

    NSString *DateTimeOriginal = [exifDic objectForKey:(NSString *)kCGImagePropertyExifDateTimeOriginal];
    NSLog(@"time is %@",DateTimeOriginal);

    CFRelease(metaDataDicRef);
    CFRelease(imgSource);
}

首先，需要用到CGImageSourceRef类，不能用UIImage类型(需要验证。。。)，这种CGImageSourceRef类型可以通过函数取出jpg的额外数据，这些数据叫做metaData，翻译过来就是元数据。得到的metaData是以字典形式返回的，其中的key是固定的，具体声明见下方

CFStringRef kCGImagePropertyTIFFDictionary;
CFStringRef kCGImagePropertyGIFDictionary;
CFStringRef kCGImagePropertyJFIFDictionary;
CFStringRef kCGImagePropertyExifDictionary;
CFStringRef kCGImagePropertyPNGDictionary;
CFStringRef kCGImagePropertyIPTCDictionary;
CFStringRef kCGImagePropertyGPSDictionary;
CFStringRef kCGImagePropertyRawDictionary;
CFStringRef kCGImagePropertyCIFFDictionary;
CFStringRef kCGImageProperty8BIMDictionary;
CFStringRef kCGImagePropertyDNGDictionary;
CFStringRef kCGImagePropertyExifAuxDictionary;

这些key中，有许多key对应的对象还是一个字典，比如kCGImagePropertyExifDictionary所对应的对象包含一下key值

const CFStringRef kCGImagePropertyExifExposureTime;
const CFStringRef kCGImagePropertyExifFNumber;
const CFStringRef kCGImagePropertyExifExposureProgram;
const CFStringRef kCGImagePropertyExifSpectralSensitivity;
const CFStringRef kCGImagePropertyExifISOSpeedRatings;
const CFStringRef kCGImagePropertyExifOECF;
const CFStringRef kCGImagePropertyExifVersion;
const CFStringRef kCGImagePropertyExifDateTimeOriginal;
const CFStringRef kCGImagePropertyExifDateTimeDigitized;
const CFStringRef kCGImagePropertyExifComponentsConfiguration;
const CFStringRef kCGImagePropertyExifCompressedBitsPerPixel;
const CFStringRef kCGImagePropertyExifShutterSpeedValue;
const CFStringRef kCGImagePropertyExifApertureValue;
const CFStringRef kCGImagePropertyExifBrightnessValue;
const CFStringRef kCGImagePropertyExifExposureBiasValue;
const CFStringRef kCGImagePropertyExifMaxApertureValue;
const CFStringRef kCGImagePropertyExifSubjectDistance;
const CFStringRef kCGImagePropertyExifMeteringMode;
const CFStringRef kCGImagePropertyExifLightSource;
const CFStringRef kCGImagePropertyExifFlash;
const CFStringRef kCGImagePropertyExifFocalLength;
const CFStringRef kCGImagePropertyExifSubjectArea;
const CFStringRef kCGImagePropertyExifMakerNote;
const CFStringRef kCGImagePropertyExifUserComment;
const CFStringRef kCGImagePropertyExifSubsecTime;
const CFStringRef kCGImagePropertyExifSubsecTimeOrginal;
const CFStringRef kCGImagePropertyExifSubsecTimeDigitized;
const CFStringRef kCGImagePropertyExifFlashPixVersion;
const CFStringRef kCGImagePropertyExifColorSpace;
const CFStringRef kCGImagePropertyExifPixelXDimension;
const CFStringRef kCGImagePropertyExifPixelYDimension;
const CFStringRef kCGImagePropertyExifRelatedSoundFile;
const CFStringRef kCGImagePropertyExifFlashEnergy;
const CFStringRef kCGImagePropertyExifSpatialFrequencyResponse;
const CFStringRef kCGImagePropertyExifFocalPlaneXResolution;
const CFStringRef kCGImagePropertyExifFocalPlaneYResolution;
const CFStringRef kCGImagePropertyExifFocalPlaneResolutionUnit;
const CFStringRef kCGImagePropertyExifSubjectLocation;
const CFStringRef kCGImagePropertyExifExposureIndex;
const CFStringRef kCGImagePropertyExifSensingMethod;
const CFStringRef kCGImagePropertyExifFileSource;
const CFStringRef kCGImagePropertyExifSceneType;
const CFStringRef kCGImagePropertyExifCFAPattern;
const CFStringRef kCGImagePropertyExifCustomRendered;
const CFStringRef kCGImagePropertyExifExposureMode;
const CFStringRef kCGImagePropertyExifWhiteBalance;
const CFStringRef kCGImagePropertyExifDigitalZoomRatio;
const CFStringRef kCGImagePropertyExifFocalLenIn35mmFilm;
const CFStringRef kCGImagePropertyExifSceneCaptureType;
const CFStringRef kCGImagePropertyExifGainControl;
const CFStringRef kCGImagePropertyExifContrast;
const CFStringRef kCGImagePropertyExifSaturation;
const CFStringRef kCGImagePropertyExifSharpness;
const CFStringRef kCGImagePropertyExifDeviceSettingDescription;
const CFStringRef kCGImagePropertyExifSubjectDistRange;
const CFStringRef kCGImagePropertyExifImageUniqueID;
const CFStringRef kCGImagePropertyExifGamma;
const CFStringRef kCGImagePropertyExifCameraOwnerName;
const CFStringRef kCGImagePropertyExifBodySerialNumber;
const CFStringRef kCGImagePropertyExifLensSpecification;
const CFStringRef kCGImagePropertyExifLensMake;
const CFStringRef kCGImagePropertyExifLensModel;
const CFStringRef kCGImagePropertyExifLensSerialNumber;

这里的每一个key都有具体的含义，代表了jpg的一些信息。这些key和key的值时有严格的格式限定的，你用了自己定义的key或者不符合规则的值，是不能正确地写入jpg文件的（待会要提到如何写入metaData信息）。

---

如何用UIImagePickerController拍摄照片后加入信息呢？用这个控件拍照后，默认生成的metaData信息较少，只有拍摄时间等几个信息，没有gps信息，更没有街道信息，我们需要手动加入。

#pragma mark - UIImagePickerControllerDelegate

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info

{

_mediaInfo =[NSMutableDictionarydictionaryWithDictionary:info];

if (!_locationManager) {

_locationManager = [[CLLocationManager alloc]init];

[_locationManagersetDelegate:self];

[_locationManagersetDistanceFilter:kCLDistanceFilterNone];

[_locationManagersetDesiredAccuracy:kCLLocationAccuracyBest];

}

[_locationManagerstartUpdatingLocation];

[picker dismissViewControllerAnimated:YEScompletion:^

{

}];

}

#pragma mark CLLocationManagerDelegate

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation{

[manager stopUpdatingLocation];

UIImage *originalImage= (UIImage *) [_mediaInfoobjectForKey:UIImagePickerControllerOriginalImage];

NSData *imageNSData = UIImageJPEGRepresentation(originalImage,1);

CGImageSourceRef imgSource = CGImageSourceCreateWithData((__bridge CFDataRef)imageNSData, NULL);

//this is the type of image (e.g., public.jpeg)

CFStringRef UTI = CGImageSourceGetType(imgSource);

//this will be the data CGImageDestinationRef will write into

NSMutableData *newImageData = [NSMutableDatadata];

CGImageDestinationRef destination = CGImageDestinationCreateWithData((__bridge  CFMutableDataRef)newImageData, UTI, 1, NULL);

if(!destination)

{

NSLog(@"***Could not create image destination ***");

return;

}

//get original metadata

NSDictionary *dict = [_mediaInfoobjectForKey:UIImagePickerControllerMediaMetadata];

NSMutableDictionary *metadata = [NSMutableDictionarydictionaryWithDictionary:dict];

//set gps info into metadata,we need a dictionary

NSDictionary * gpsDict=[newLocation GPSDictionary];

if (metadata && gpsDict) {

[metadata setValue:gpsDict forKey:(NSString*)kCGImagePropertyGPSDictionary];

}

//get location detail by CLGeocoder, this needs wifi

CLGeocoder *geocoder = [[CLGeocoder alloc] init];

[geocoder reverseGeocodeLocation:newLocation completionHandler:^(NSArray *placemarks, NSError *error){

if(error != nil)

{

NSLog(@"CLGeocoder error :%@ ",error);

}

else//if we can get place info ,we set it into meteData dic with kCGImagePropertyExifCameraOwnerName key

{

if(placemarks.count > 0)

{

CLPlacemark *placemark = [placemarks objectAtIndex:0];

NSMutableDictionary *eifDic = (NSMutableDictionary *)[metadata objectForKey:(NSString *)kCGImagePropertyExifDictionary];

[eifDic setObject:placemark.nameforKey:(NSString *)kCGImagePropertyExifCameraOwnerName];

}

}

//add the image contained in the image source to the destination, overidding the old metadata with our modified metadata

CGImageDestinationAddImageFromSource(destination, imgSource, 0, (__bridge  CFDictionaryRef) metadata);

BOOL success = NO;

success = CGImageDestinationFinalize(destination);

if(!success) {

NSLog(@"***Could not create data from image destination ***");

return ;

}

CFRelease(imgSource);

CFRelease(destination);

[self sendData:newImageData];

[self writeTest:newImageData];

}];

}

@implementation CLLocation (GPSDictionary)

-(NSDictionary*)GPSDictionary{

NSDateFormatter *formatter  = [[NSDateFormatteralloc] init];

[formatter setDateFormat:@"hh:mm:ss.SS"];

CLLocation *location=self;

NSDictionary *gpsDict   = [NSDictionarydictionaryWithObjectsAndKeys:

[NSNumbernumberWithFloat:fabs(location.coordinate.latitude)], kCGImagePropertyGPSLatitude,

((location.coordinate.latitude >= 0) ? @"N" : @"S"), kCGImagePropertyGPSLatitudeRef,

[NSNumbernumberWithFloat:fabs(location.coordinate.longitude)], kCGImagePropertyGPSLongitude,

((location.coordinate.longitude >= 0) ? @"E" : @"W"), kCGImagePropertyGPSLongitudeRef,

[formatter stringFromDate:[location timestamp]], kCGImagePropertyGPSTimeStamp,

nil];

NSLog(@"gpsDict i %@",gpsDict);

return gpsDict;

}

@end

上面代码需要手动改改，它的最终目的就是用 CGImageDestinationAddImageFromSource(destination, imgSource, 0, (__bridge CFDictionaryRef) metadata);函数用新的metaData信息生成新的jpg数据。

其中gps数据用了系统自定义的key值写入，街道信息没有找到合适的key，就冒用了kCGImagePropertyExifCameraOwnerName这个key。