#import <AssetsLibrary/AssetsLibrary.h>

-(void)getImgs{
   
    dispatch_async(dispatch_get_main_queue(), ^{
        NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
       
       
        ALAssetsLibraryAccessFailureBlock failureblock = ^(NSError *myerror){
            NSLog(@"相冊訪問失敗 =%@", [myerror localizedDescription]);
            if ([myerror.localizedDescription rangeOfString:@"Global denied access"].location!=NSNotFound) {
                  NSLog(@"無法訪問相冊.請在'設置->定位服務'設置為打開狀態.");
            }else{
                NSLog(@"相冊訪問失敗.");
            }
        };
       
        ALAssetsGroupEnumerationResultsBlock groupEnumerAtion = ^(ALAsset *result, NSUInteger index, BOOL *stop){
            if (result!=NULL) {
       
                if ([[result valueForProperty:ALAssetPropertyType] isEqualToString:ALAssetTypePhoto]) {
                   
                    NSString *urlstr=[NSString stringWithFormat:@"%@",result.defaultRepresentation.url];//圖片的url
/*result.defaultRepresentation.fullScreenImage//圖片的大圖
result.thumbnail                             //圖片的縮略圖小圖
//                    NSRange range1=[urlstr rangeOfString:@"id="];
//                    NSString *resultName=[urlstr substringFromIndex:range1.location+3];
//                    resultName=[resultName stringByReplacingOccurrencesOfString:@"&ext=" withString:@"."];//格式demo:123456.png
*/
                   
                  [self._dataArray addObject:urlstr];
                }
            }
          
        };
        ALAssetsLibraryGroupsEnumerationResultsBlock
        libraryGroupsEnumeration = ^(ALAssetsGroup* group, BOOL* stop){
           
            if (group == nil)
            {
               
            }
           
            if (group!=nil) {
                NSString *g=[NSString stringWithFormat:@"%@",group];//獲取相簿的組
                NSLog(@"gg:%@",g);//gg:ALAssetsGroup - Name:Camera Roll, Type:Saved Photos, Assets count:71

                NSString *g1=[g substringFromIndex:16 ] ;
                NSArray *arr=[[NSArray alloc] init];
                arr=[g1 componentsSeparatedByString:@","];
                NSString *g2=[[arr objectAtIndex:0] substringFromIndex:5];
                if ([g2 isEqualToString:@"Camera Roll"]) {
                    g2=@"相機膠卷";
                }
                NSString *groupName=g2;//組的name
               
                [group enumerateAssetsUsingBlock:groupEnumerAtion];
            }
           
        };
       
        ALAssetsLibrary* library = [[ALAssetsLibrary alloc] init];
        [library enumerateGroupsWithTypes:ALAssetsGroupAll
                               usingBlock:libraryGroupsEnumeration
                             failureBlock:failureblock];
        [library release];     
        [pool release];
    }); 
   
}

//------------------------根據圖片的url反取圖片－－－－－

  ALAssetsLibrary *assetLibrary=[[ALAssetsLibrary alloc] init];
NSURL *url=[NSURL URLWithString:urlStr];
[assetLibrary assetForURL:url resultBlock:^(ALAsset *asset)  {
                UIImage *image=[UIImage imageWithCGImage:asset.thumbnail];
                cellImageView.image=image;
          
                }failureBlock:^(NSError *error) {
                    NSLog(@"error=%@",error);
            }
             ];
//－－－－－－－－－－－－－－－－－－－－－ 

摘自  shijiucdy的專欄