媒体层图形技术之AssetsLibrary 学习笔记
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
– valueForProperty:(1.ALAssetPropertyType 资源的类型（照片，视频）2.ALAssetPropertyLocation 资源地理位置（无位置信息返回null）3.ALAssetPropertyDuation 播放时长（照片返回ALErorInvalidProperty)- 4.ALAssetPropertyOrientation 方向（共有8个方向，参见：ALAssetOrientation)
- 5.ALAssetPropertyDate 拍摄时间（包含了年与日时分秒）
- 6.ALAssetPropertyRepresentations 描述（打印看了下，只有带后缀的名称）
- 7.ALAssetPropertyURLs（返回一个字典，键值分别是文件名和文件的url）
- 8.ALAssetPropertyAssetURL 文件的url )
editableproperty（指示资源是否可以编辑，只读属性)originalAssetproperty（原始资源。若没有保存修改后资源，则原始资源为nil）
Accessing Representations
– defaultRepresentation– representationForUTI:– thumbnail（小正方形的缩略图）– aspectRatioThumbnail（按原始资源长宽比例的缩略图）
Setting New Image and Video Data
– setImageData:metadata:completionBlock:用给定的image data 替换接收者的image data。- – setVideoAtPath:completionBlock:
- 用给定的URL的video 替换接收者的video data。
Saving to the Saved Photos Album
– writeModifiedImageDataToSavedPhotosAlbum:metadata:completionBlock:保存image data到Saved Photos album– writeModifiedVideoAtPathToSavedPhotosAlbum:completionBlock:
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。
Getting Image Representations
– CGImageWithOptions:– fullResolutionImage（完全分辨率的图片）– fullScreenImage（满屏的图片）
Getting Image Attributes
– orientation（文件方向）– scale（长宽比例）– filename（文件名字）
Getting Raw Data
– size（文件尺寸，以byte为单位）– getBytes:fromOffset:length:error:
Getting Metadata
– UTI
– metadata
- Getting an URL
- – url
//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）
– enumerateAssetsUsingBlock:（用一个block来遍历组里的资源）– enumerateAssetsWithOptions:usingBlock:（在枚举选项的条件下，用一个block来遍历组里的资源）– enumerateAssetsAtIndexes:options:usingBlock:（在枚举选项的条件下，用一个block来遍历组里特定index的资源）
- (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:UICollectionViewScrollPositionTop
animated:YES];
}
};
[self.assetsGroup enumerateAssetsUsingBlock:resultsBlock];
}
Adding Assets（添加资源）
– addAsset:（添加一个已存在的asset到接收者。返回yes成功；反之，失败。）editableproperty（指示程序是否可以编辑组，只读属性，打印看了一下，系统自带的是不能编辑的，其它可以编辑）
Filtering（过滤）
– numberOfAssets（返回组过滤器条件下的资源个数，若没有设置过滤器，则返回组里的资源个数）– setAssetsFilter:（设置组的过滤器）
Accessing Properties（访问属性）
– valueForProperty:（通过组属性名称，获取组属性：组名称，组类型，组永久性ID,组URL）– posterImage（组的封面）
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id
NSLog(@"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:ALAssetsGroupSavedPhotos
usingBlock:resultsBlock
failureBlock:failureBlock];
// Then all other groups
NSUInteger type =
ALAssetsGroupLibrary | ALAssetsGroupAlbum | ALAssetsGroupEvent |
ALAssetsGroupFaces | ALAssetsGroupPhotoStream;
[self.assetsLibrary enumerateGroupsWithTypes:type
usingBlock:resultsBlock
failureBlock: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);
}];