Get all images (full size) from Image gellery in iOS

ViewController.h

#import <UIKit/UIKit.h>
#import <AssetsLibrary/AssetsLibrary.h>

@interface ViewController : UIViewController<UICollectionViewDataSource, UICollectionViewDelegate>
{
    ALAssetsLibrary *library;
    NSArray *imageArray;
    NSMutableArray *mutableArray;

    IBOutlet UICollectionView *collectionView;
}

-(void)allPhotosCollected:(NSArray*)imgArray;
@end

ViewController.m

#import "ViewController.h"
#import "PhotoCollectionViewCell.h"


static int count=0;

@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    [self getAllPictures];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
} 
#pragma mark - read image from ios gallery
-(void)getAllPictures
{
    imageArray=[[NSArray alloc] init];
    mutableArray =[[NSMutableArray alloc]init];
    NSMutableArray* assetURLDictionaries = [[NSMutableArray alloc] init];
    
    library = [[ALAssetsLibrary alloc] init];
    
    void (^assetEnumerator)( ALAsset *, NSUInteger, BOOL *) = ^(ALAsset *result, NSUInteger index, BOOL *stop) {
        if(result != nil) {
            if([[result valueForProperty:ALAssetPropertyType] isEqualToString:ALAssetTypePhoto]) {
                [assetURLDictionaries addObject:[result valueForProperty:ALAssetPropertyURLs]];
                
                NSURL *url= (NSURL*) [[result defaultRepresentation]url];
                
                [library assetForURL:url
                         resultBlock:^(ALAsset *asset) {
                             [mutableArray addObject:[UIImage imageWithCGImage:[[asset defaultRepresentation] fullScreenImage]]];
                             
                             if ([mutableArray count]==count)
                             {
                                 imageArray=[[NSArray alloc] initWithArray:mutableArray];
                                 [self allPhotosCollected:imageArray];
                             }
                         }
                        failureBlock:^(NSError *error){ NSLog(@"operation was not successfull!"); } ];
                
            }
        }
    };
    
    NSMutableArray *assetGroups = [[NSMutableArray alloc] init];
    
    void (^ assetGroupEnumerator) ( ALAssetsGroup *, BOOL *)= ^(ALAssetsGroup *group, BOOL *stop) {
        if(group != nil) {
            [group enumerateAssetsUsingBlock:assetEnumerator];
            [assetGroups addObject:group];
            count=[group numberOfAssets];
        }
    };
    
    assetGroups = [[NSMutableArray alloc] init];
    
    [library enumerateGroupsWithTypes:ALAssetsGroupAll
                           usingBlock:assetGroupEnumerator
                         failureBlock:^(NSError *error) {NSLog(@"There is an error");}];
}

-(void)allPhotosCollected:(NSArray*)imgArray
{
    //write your code here after getting all the photos from library...
    NSLog(@"all pictures(%d) are %@",imgArray.count,imgArray);
   // all UIImage objects are available in imageArray or imgArray
// Do with that image data imageArray 
}