choudang的专栏

转载自 http://m.blog.csdn.net/blog/choudang/28274519

1.ALAsset

ALAsset类代表相册中的每个资源文件，可以通过它获取资源文件的相关信息还能修改和新建资源文件

Asset Properties

Accessing Representations

Setting New Image and Video Data

Saving to the Saved Photos Album

保存video到Saved Photos album的指定路径

//通过ALAsset获取相对应的资源，获取图片的等比缩略图，原图的等比缩略CGImageRef ratioThum = [asset aspectRatioThumbnail];//获取相片的缩略图，该缩略图是相册中每张照片的poster图CGImageRef thum = [asset thumbnail];UIImage* rti = [UIImage imageWithCGImage:ratioThum];UIImage* ti = [UIImage imageWithCGImage:thum];UIImageView* v1 = [[UIImageView alloc]initWithFrame:CGRectMake(20, 100, 120, 200)];v1.image = rti;v1.contentMode = UIViewContentModeScaleAspectFit;UIImageView* v2 = [[UIImageView alloc]initWithFrame:CGRectMake(180, 100, 120, 200)];v2.image = ti;v2.contentMode = UIViewContentModeScaleAspectFit;[self.view addSubview:v1];[self.view addSubview:v2];

UIImage* ni = [UIImage imageNamed:@"new.png"];//修改指定路径的图片资源内容，替换掉原来的内容[asset setImageData:UIImageJPEGRepresentation(ni, 1.0) metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) {NSLog(@"new:%@",assetURL);}];

//根据给定的图片内容，重新生成一张新图[asset writeModifiedImageDataToSavedPhotosAlbum:UIImageJPEGRepresentation(ni, 1.0) metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) {NSLog(@"new:%@",assetURL);}];

2.ALAssetRepresentation

ALAssetRepresentation类代表相册中每个资源文件的详细信息，可以通过它获取资源的大小，名字，路径等详细信息。

ALAssetRepresentation

---------------------------------------------------------------------------

ALAssetRepresentation对象封装了一个给定ALAsset对象的陈述。

一个在资源库中给定的asset可能有不止一个陈述。比如，如果一个相机提供RAW和JPEG格式的图像版本，

asset将有两个陈述版本，一个是RAW的,一个是JPEG的。

Getting Image Representations

Getting Image Attributes

Getting Raw Data

Getting Metadata

– UTI

– metadata

 //获取资源图片的详细资源信息ALAssetRepresentation* representation = [asset defaultRepresentation];//获取资源图片的长宽CGSize dimension = [representation dimensions];//获取资源图片的高清图[representation fullResolutionImage];//获取资源图片的全屏图[representation fullScreenImage];//获取资源图片的名字NSString* filename = [representation filename];NSLog(@"filename:%@",filename);//缩放倍数[representation scale];//图片资源容量大小[representation size];//图片资源原数据[representation metadata];//旋转方向[representation orientation];//资源图片url地址，该地址和ALAsset通过ALAssetPropertyAssetURL获取的url地址是一样的NSURL* url = [representation url];NSLog(@"url:%@",url);//资源图片uti，唯一标示符NSLog(@"uti:%@",[representation UTI]);

3.ALAssetsFilter

过滤器筛选出想要展现的资源：图片资源、视频资源

// Get all photos assets in the assets group.
+ (ALAssetsFilter *)allPhotos;
// Get all video assets in the assets group.
+ (ALAssetsFilter *)allVideos;
// Get all assets in the group.
+ (ALAssetsFilter *)allAssets;

4.ALAssetsGroup

Enumerating Assets（遍历资源）

- (void)setupAssets
{self.title = [self.assetsGroup valueForProperty:ALAssetsGroupPropertyName];if (!self.assets)self.assets = [[NSMutableArray alloc] init];else[self.assets removeAllObjects];ALAssetsGroupEnumerationResultsBlock resultsBlock = ^(ALAsset *asset, NSUInteger index, BOOL *stop) {if (asset){[self.assets addObject:asset];NSString *type = [asset valueForProperty:ALAssetPropertyType];if ([type isEqual:ALAssetTypePhoto])self.numberOfPhotos ++;if ([type isEqual:ALAssetTypeVideo])self.numberOfVideos ++;}else if (self.assets.count > 0){[self.collectionView reloadData];[self.collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:self.assets.count-1 inSection:0]atScrollPosition:UICollectionViewScrollPositionTopanimated:YES];}};[self.assetsGroup enumerateAssetsUsingBlock:resultsBlock];
}

Adding Assets（添加资源）

Filtering（过滤）

Accessing Properties（访问属性）

5.ALAssetsLibrary

代表系统中整个资源库，使用它可以访问资源库中的资源和保存照片，视频等功能。

 //判断当前应用是否能访问相册资源/*typedef NS_ENUM(NSInteger, ALAuthorizationStatus) {ALAuthorizationStatusNotDetermined = 0, 用户尚未做出了选择这个应用程序的问候ALAuthorizationStatusRestricted,        此应用程序没有被授权访问的照片数据。可能是家长控制权限。ALAuthorizationStatusDenied,            用户已经明确否认了这一照片数据的应用程序访问.ALAuthorizationStatusAuthorized         用户已授权应用访问照片数据.}*/int author = [ALAssetsLibrary authorizationStatus];NSLog(@"author type:%d",author);//关闭监听共享照片流产生的频繁通知信息[ALAssetsLibrary disableSharedPhotoStreamsSupport];//创建一个相册到相册资源中，并通过block返回创建成功的相册ALAssetsGroup[_library addAssetsGroupAlbumWithName:@"test" resultBlock:^(ALAssetsGroup *group) {//NSString *const ALAssetsGroupPropertyName;//NSString *const ALAssetsGroupPropertyType;//NSString *const ALAssetsGroupPropertyPersistentID;//NSString *const ALAssetsGroupPropertyURL;//查看相册的名字NSLog(@"ALAssetsGroupPropertyName:%@",[group valueForProperty:ALAssetsGroupPropertyName]);//查看相册的类型NSLog(@"ALAssetsGroupPropertyType:%@",[group valueForProperty:ALAssetsGroupPropertyType]);//查看相册的存储idNSLog(@"ALAssetsGroupPropertyPersistentID:%@",[group valueForProperty:ALAssetsGroupPropertyPersistentID]);//查看相册存储的位置地址NSLog(@"ALAssetsGroupPropertyURL:%@",[group valueForProperty:ALAssetsGroupPropertyURL]);groupURL = [group valueForProperty:ALAssetsGroupPropertyURL];} failureBlock:^(NSError *error) {}];

新添加了一个名为test的相册

    //通过url地址在相册资源中获取该地址的资源文件ALAsset，有可能是相片或视频
    [_library assetForURL:[NSURL URLWithString:@""] resultBlock:^(ALAsset *asset) {
        /*
         NSString *const ALAssetPropertyType;
         NSString *const ALAssetPropertyLocation;
         NSString *const ALAssetPropertyDuration;
         NSString *const ALAssetPropertyOrientation;
         NSString *const ALAssetPropertyDate;
         NSString *const ALAssetPropertyRepresentations;
         NSString *const ALAssetPropertyURLs;
         NSString *const ALAssetPropertyAssetURL;
         */
        //查看资源的地理位置信息
        NSLog(@"ALAssetPropertyLocation:%@",[asset valueForProperty:ALAssetPropertyLocation]);
        //如果资源是视频，查看视频的时长
        NSLog(@"ALAssetPropertyDuration:%@",[asset valueForProperty:ALAssetPropertyDuration]);
        //查看资源的方向，图片的旋转方向
        NSLog(@"ALAssetPropertyOrientation:%@",[asset valueForProperty:ALAssetPropertyOrientation]);
        //查看资源的创建时间
        NSLog(@"ALAssetPropertyDate:%@",[asset valueForProperty:ALAssetPropertyDate]);
        //查看资源的描述信息
        NSLog(@"ALAssetPropertyRepresentations:%@",[asset valueForProperty:ALAssetPropertyRepresentations]);
        NSLog(@"ALAssetPropertyURLs:%@",[asset valueForProperty:ALAssetPropertyURLs]);
        //查看资源的url路径
        NSLog(@"ALAssetPropertyAssetURL:%@",[asset valueForProperty:ALAssetPropertyAssetURL]);
    } failureBlock:^(NSError *error) {

    }];
    //通过url地址获取相册资源中的一个相册
    [_library groupForURL:groupURL resultBlock:^(ALAssetsGroup *group) {
        NSLog(@"ALAssetsGroupPropertyName:%@",[group valueForProperty:ALAssetsGroupPropertyName]);
    } failureBlock:^(NSError *error) {

    }];

//根据选择的类型遍历相册资源中的相对应类型的所有相册，其中stop行参是指针，表示是否停止迭代，当赋值为false则停止
    /*
     enum {
     ALAssetsGroupLibrary        = (1 << 0),
     ALAssetsGroupAlbum          = (1 << 1),
     ALAssetsGroupEvent          = (1 << 2),
     ALAssetsGroupFaces          = (1 << 3),
     ALAssetsGroupSavedPhotos    = (1 << 4),
     ALAssetsGroupPhotoStream    = (1 << 5),
     ALAssetsGroupAll            = 0xFFFFFFFF,
     };
     */
    [_library enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
        NSLog(@"group name:%@",[group valueForProperty:ALAssetsGroupPropertyName]);
    } failureBlock:^(NSError *error) {

    }];

利用资源库得枚举函数把资源组分类，代码如下：

- (void)setupGroup
{if (!self.assetsLibrary)self.assetsLibrary = [self.class defaultAssetsLibrary];if (!self.groups)self.groups = [[NSMutableArray alloc] init];else[self.groups removeAllObjects];CTAssetsPickerController *picker = (CTAssetsPickerController *)self.navigationController;ALAssetsFilter *assetsFilter = picker.assetsFilter;ALAssetsLibraryGroupsEnumerationResultsBlock resultsBlock = ^(ALAssetsGroup *group, BOOL *stop) {if (group){[group setAssetsFilter:assetsFilter];if (group.numberOfAssets > 0)[self.groups addObject:group];}else{[self reloadData];}};ALAssetsLibraryAccessFailureBlock failureBlock = ^(NSError *error) {[self showNotAllowed];};// Enumerate Camera roll first[self.assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupSavedPhotosusingBlock:resultsBlockfailureBlock:failureBlock];// Then all other groupsNSUInteger type =ALAssetsGroupLibrary | ALAssetsGroupAlbum | ALAssetsGroupEvent |ALAssetsGroupFaces | ALAssetsGroupPhotoStream;[self.assetsLibrary enumerateGroupsWithTypes:typeusingBlock:resultsBlockfailureBlock:failureBlock];
}

其中得[self.class defaultAssetsLibrary]为单列形式：

#pragma mark - ALAssetsLibrary+ (ALAssetsLibrary *)defaultAssetsLibrary
{static dispatch_once_t pred = 0;static ALAssetsLibrary *library = nil;dispatch_once(&pred, ^{library = [[ALAssetsLibrary alloc] init];});return library;
}

    //保存图片到系统默认的相册中，使用nsdata的形式，并返回照片的url地址
    [_library writeImageDataToSavedPhotosAlbum:nil metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) {

    }];
    //保存图片到系统默认的相册中，使用cgimageref的形式，并返回照片的url地址
    [_library writeImageToSavedPhotosAlbum:nil metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) {

    }];

    //保存图片到系统默认的相册中，使用cgimageref的形式，并且选择图片以什么旋转方向的形式保存，并返回照片的url地址
    /*
     typedef enum {
     ALAssetOrientationUp,            // default orientation
     ALAssetOrientationDown,          // 180 deg rotation
     ALAssetOrientationLeft,          // 90 deg CCW
     ALAssetOrientationRight,         // 90 deg CW
     ALAssetOrientationUpMirrored,    // as above but image mirrored along other axis. horizontal flip
     ALAssetOrientationDownMirrored, // horizontal flip
     ALAssetOrientationLeftMirrored, // vertical flip
     ALAssetOrientationRightMirrored, // vertical flip
     } ALAssetOrientation;
     */
    UIImage* image = [UIImage imageNamed:@"test.png"];
    [_library writeImageToSavedPhotosAlbum:[image CGImage] orientation:ALAssetOrientationLeft completionBlock:^(NSURL *assetURL, NSError *error) {
        NSLog(@"save image:%@",assetURL);
    }];