How to store high quality image in iphone Library?

I have taken 1 high quality image and stored it to some place

 UIImage *image = [[UIImage alloc] initWithData:imageData];
 NSArray *docDirs = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSAllDomainsMask, YES);
 NSString *docDir = [docDirs objectAtIndex:0];
 BOOL success = [UIImagePNGRepresentation(image) writeToFile:[docDir stringByAppendingPathComponent:@"test11.png"] atomically:YES];

I can see from xcode organizer the image resolution is very high quality. Dimension: 2592 × 1936 ... size 6.1MB

My problem is how can I store high quality image in iphone Library. I am strictly not allowed to store compressed image. I have to s开发者_如何学运维tore only HD high quality image.

Please do not reply with scaleAndRotateImage functions because it will compress image.

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ALAssetsLibrary class will let you do that.