在iOS4.1上保存带有照片的地理标签信息

Question

我在尝试使用iOS4.1上的地理标签信息将照片保存到相机卷时出现重大问题。我正在使用以下ALAssetsLibrary API：

- (void)writeImageDataToSavedPhotosAlbum:(NSData *)imageData 
           metadata:(NSDictionary *)metadata 
         completionBlock:(ALAssetsLibraryWriteImageCompletionBlock)completionBlock 

我有GPS坐标，我希望将照片保存为输入。不幸的是，没有文档或示例代码描述了如何形成封装GPS坐标的元数据NSDictionary。有人可以发布已知工作的示例代码吗？

我也尝试过使用iPhone Exif库来保存imageData中的地理信息，而不是使用元数据，但不幸的是iPhone Exif库崩溃了。任何帮助是极大的赞赏。

Answer 1

经过一番搜索，我发现并适应这个

这原来cclocation数据到合适的NSDictionary

#import <ImageIO/ImageIO.h> 

+(NSMutableDictionary *)updateExif:(CLLocation *)currentLocation{ 


    NSMutableDictionary* locDict = [[NSMutableDictionary alloc] init]; 


    CLLocationDegrees exifLatitude = currentLocation.coordinate.latitude; 
    CLLocationDegrees exifLongitude = currentLocation.coordinate.longitude; 

    [locDict setObject:currentLocation.timestamp forKey:(NSString*)kCGImagePropertyGPSTimeStamp]; 

    if (exifLatitude <0.0){ 
     exifLatitude = exifLatitude*(-1); 
     [locDict setObject:@"S" forKey:(NSString*)kCGImagePropertyGPSLatitudeRef]; 
    }else{ 
     [locDict setObject:@"N" forKey:(NSString*)kCGImagePropertyGPSLatitudeRef]; 
    } 
    [locDict setObject:[NSNumber numberWithFloat:exifLatitude] forKey:(NSString*)kCGImagePropertyGPSLatitude]; 

    if (exifLongitude <0.0){ 
     exifLongitude=exifLongitude*(-1); 
     [locDict setObject:@"W" forKey:(NSString*)kCGImagePropertyGPSLongitudeRef]; 
    }else{ 
     [locDict setObject:@"E" forKey:(NSString*)kCGImagePropertyGPSLongitudeRef]; 
    } 
    [locDict setObject:[NSNumber numberWithFloat:exifLongitude] forKey:(NSString*) kCGImagePropertyGPSLongitude]; 


    return [locDict autorelease]; 

} 

然后我把它添加到您通过相机获得现有的元数据（不默认情况下，具备GPS数据）

我得到这样

-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info{ 
    [imageMetaData setDictionary:[[info objectForKey:UIImagePickerControllerMediaMetadata] copy]]; 
} 

原来的元数据

然后我添加上一个方法产生的gps字典。

[imageMetaData setObject:currentLocation forKey:(NSString*)kCGImagePropertyGPSDictionary];   

    [library writeImageToSavedPhotosAlbum:[viewImage CGImage] metadata:imageMetaData completionBlock:photoCompblock]; 

Answer 2

这里是代码从CLLocation对象复制所有可用的信息转换成适当的格式用于GPS元数据字典：

- (NSDictionary *)getGPSDictionaryForLocation:(CLLocation *)location { 
    NSMutableDictionary *gps = [NSMutableDictionary dictionary]; 

    // GPS tag version 
    [gps setObject:@"2.2.0.0" forKey:(NSString *)kCGImagePropertyGPSVersion]; 

    // Time and date must be provided as strings, not as an NSDate object 
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init]; 
    [formatter setDateFormat:@"HH:mm:ss.SSSSSS"]; 
    [formatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]]; 
    [gps setObject:[formatter stringFromDate:location.timestamp] forKey:(NSString *)kCGImagePropertyGPSTimeStamp]; 
    [formatter setDateFormat:@"yyyy:MM:dd"]; 
    [gps setObject:[formatter stringFromDate:location.timestamp] forKey:(NSString *)kCGImagePropertyGPSDateStamp]; 
    [formatter release]; 

    // Latitude 
    CGFloat latitude = location.coordinate.latitude; 
    if (latitude < 0) { 
     latitude = -latitude; 
     [gps setObject:@"S" forKey:(NSString *)kCGImagePropertyGPSLatitudeRef]; 
    } else { 
     [gps setObject:@"N" forKey:(NSString *)kCGImagePropertyGPSLatitudeRef]; 
    } 
    [gps setObject:[NSNumber numberWithFloat:latitude] forKey:(NSString *)kCGImagePropertyGPSLatitude]; 

    // Longitude 
    CGFloat longitude = location.coordinate.longitude; 
    if (longitude < 0) { 
     longitude = -longitude; 
     [gps setObject:@"W" forKey:(NSString *)kCGImagePropertyGPSLongitudeRef]; 
    } else { 
     [gps setObject:@"E" forKey:(NSString *)kCGImagePropertyGPSLongitudeRef]; 
    } 
    [gps setObject:[NSNumber numberWithFloat:longitude] forKey:(NSString *)kCGImagePropertyGPSLongitude]; 

    // Altitude 
    CGFloat altitude = location.altitude; 
    if (!isnan(altitude)){ 
     if (altitude < 0) { 
      altitude = -altitude; 
      [gps setObject:@"1" forKey:(NSString *)kCGImagePropertyGPSAltitudeRef]; 
     } else { 
      [gps setObject:@"0" forKey:(NSString *)kCGImagePropertyGPSAltitudeRef]; 
     } 
     [gps setObject:[NSNumber numberWithFloat:altitude] forKey:(NSString *)kCGImagePropertyGPSAltitude]; 
    } 

    // Speed, must be converted from m/s to km/h 
    if (location.speed >= 0){ 
     [gps setObject:@"K" forKey:(NSString *)kCGImagePropertyGPSSpeedRef]; 
     [gps setObject:[NSNumber numberWithFloat:location.speed*3.6] forKey:(NSString *)kCGImagePropertyGPSSpeed]; 
    } 

    // Heading 
    if (location.course >= 0){ 
     [gps setObject:@"T" forKey:(NSString *)kCGImagePropertyGPSTrackRef]; 
     [gps setObject:[NSNumber numberWithFloat:location.course] forKey:(NSString *)kCGImagePropertyGPSTrack]; 
    } 

    return gps; 
} 

指定由该方法作为返回值的字典为kCGImagePropertyGPSDictionary键在元数据字典中，您传递给writeImageDataToSavedPhotosAlbum:metadata:completionBlock:或CGImageDestinationAddImage()。

Answer 3

我使用此代码并创建了一个NSMutableDictionary以帮助将地理标签和其他元数据保存到图像。点击这里，查看我的博客文章：

http://blog.codecropper.com/2011/05/adding-metadata-to-ios-images-the-easy-way/

Answer 4

这里的要点上一个方便CLLocation类别做这一切为您：

https://gist.github.com/phildow/6043486