我在尝试在 iOS 4.1 上将带有地理标记信息的照片保存到相机胶卷时遇到重大问题。我正在使用以下资产库 API:
- (void)writeImageDataToSavedPhotosAlbum:(NSData *)imageData
metadata:(NSDictionary *)metadata
completionBlock:(ALAssetsLibraryWriteImageCompletionBlock)completionBlock
我有 GPS 坐标,希望将其与照片一起保存作为输入。不幸的是,没有文档或示例代码来描述如何形成封装 GPS 坐标的元数据 NSDictionary。有人可以发布已知有效的示例代码吗?
我还尝试使用 iPhone Exif 库将地理信息保存在 imageData 中,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。
以下代码用于将 CLLocation 对象中的所有可用信息复制为 GPS 元数据字典的正确格式:
- (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;
}
将此方法返回的字典指定为kCGImagePropertyGPSDictionary
输入您传递给的元数据字典writeImageDataToSavedPhotosAlbum:metadata:completionBlock:
or CGImageDestinationAddImage()
.
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