系统自建相册并保存图片

- (void)saveImageToAlbum:(UIImage *)image albumName:(NSString *)albumName
{
    if (albumName != nil && ![albumName isEqualToString:@""]) {
        [self createAlbumInPhoneAlbum:albumName];
    }


    [self saveToAlbumWithMetadata:nil imageData:UIImagePNGRepresentation(image) customAlbumName:albumName completionBlock:^
     {
         //这里可以创建添加成功的方法
         [ErrorMessage showErrorMessage:@"下载成功" inView:[UIApplication sharedApplication].keyWindow];

     }failureBlock:^(NSError *error)
     {
         //处理添加失败的方法显示alert让它回到主线程执行，不然那个框框死活不肯弹出来
         dispatch_async(dispatch_get_main_queue(), ^{

             //添加失败一般是由用户不允许应用访问相册造成的，这边可以取出这种情况加以判断一下
             if([error.localizedDescription rangeOfString:@"User denied access"].location != NSNotFound ||[error.localizedDescription rangeOfString:@"用户拒绝访问"].location!=NSNotFound){

                 UIAlertView *alert=[[UIAlertView alloc]initWithTitle:error.localizedDescription message:error.localizedFailureReason delegate:nil cancelButtonTitle:NSLocalizedString(@"ok", nil) otherButtonTitles: nil];

                 [alert show];

             }
         });
     }];
} 

- (void)saveToAlbumWithMetadata:(NSDictionary *)metadata
                      imageData:(NSData *)imageData
                customAlbumName:(NSString *)customAlbumName
                completionBlock:(void (^)(void))completionBlock
                   failureBlock:(void (^)(NSError *error))failureBlock
{

    ALAssetsLibrary *assetsLibrary = [[ALAssetsLibrary alloc] init];

    void (^AddAsset)(ALAssetsLibrary *, NSURL *) = ^(ALAssetsLibrary *assetsLibrary, NSURL *assetURL) {
        [assetsLibrary assetForURL:assetURL resultBlock:^(ALAsset *asset) {
            [assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:^(ALAssetsGroup *group, BOOL *stop) {

                if ([[group valueForProperty:ALAssetsGroupPropertyName] isEqualToString:customAlbumName]) {
                    [group addAsset:asset];
                    if (completionBlock) {
                        completionBlock();
                    }
                }
            } failureBlock:^(NSError *error) {
                if (failureBlock) {
                    failureBlock(error);
                }
            }];
        } failureBlock:^(NSError *error) {
            if (failureBlock) {
                failureBlock(error);
            }
        }];
    };

    [assetsLibrary writeImageDataToSavedPhotosAlbum:imageData metadata:metadata completionBlock:^(NSURL *assetURL, NSError *error) {
        if (customAlbumName) {
            [assetsLibrary addAssetsGroupAlbumWithName:customAlbumName resultBlock:^(ALAssetsGroup *group) {
                if (group) {
                    [assetsLibrary assetForURL:assetURL resultBlock:^(ALAsset *asset) {
                        [group addAsset:asset];
                        if (completionBlock) {
                            completionBlock();
                        }
                    } failureBlock:^(NSError *error) {
                        if (failureBlock) {
                            failureBlock(error);
                        }
                    }];
                } else {
                    AddAsset(assetsLibrary, assetURL);
                }
            } failureBlock:^(NSError *error) {
                AddAsset(assetsLibrary, assetURL);
            }];
        } else {
            if (completionBlock) {
                completionBlock();
            }
        }
    }];
}