ALAssetsLibrary，ALAssetsGroup，ALAsset，ALAssetRepresentation用法详解
2014-05-24 17:20
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ALAssetsLibrary类是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。
ALAssetsLibrary被封装在 框架中。所以，我们在使用时，需要引入该框架。
需添加AssetsLibrary.framework
然后引入
#import <AssetsLibrary/ALAsset.h>
#import <AssetsLibrary/ALAssetsLibrary.h>
#import <AssetsLibrary/ALAssetsGroup.h>
#import <AssetsLibrary/ALAssetRepresentation.h>
_library = [[ALAssetsLibrary alloc]init];
//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
[NSThread sleepForTimeInterval:0.5];
//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) {
}];
//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);
}];
/*
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);
//通过ALAssetsLibrary迭代取出所有相册
[_library enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
NSString* groupname = [group valueForProperty:ALAssetsGroupPropertyName];
//如果相册的名称是test的时候，对其进行操作
if ([groupname isEqualToString:@"test"]) {
//设置相册组的筛选条件，ALAssetsFilter类表示筛选条件，allPhotos代表相册只包含相片，allVideos代表只包含视频，allAssets代表包含所有资源
[group setAssetsFilter:[ALAssetsFilter allPhotos]];
//通过刚保存的照片的url，把保存到默认相册的照片也保存到test相册中
[_library assetForURL:assetURL resultBlock:^(ALAsset *asset) {
//添加资源到指定的相册
[group addAsset:asset];
//获取相册中一共的资源数量
int count = [group numberOfAssets];
NSLog(@"count:%d",count);
dispatch_queue_t main = dispatch_get_main_queue();
dispatch_async(main, ^{
//获取相册的封面图片
CGImageRef poster = [group posterImage];
[imageView setImage:[UIImage imageWithCGImage:poster]];
});
//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]);
//按遍历顺序获取指定索引的资源，遍历顺序可以是先序或倒序
/*
enum {
NSEnumerationConcurrent = (1UL << 0),
NSEnumerationReverse = (1UL << 1),
};
typedef NSUInteger NSEnumerationOptions;
*/
[group enumerateAssetsAtIndexes:[NSIndexSet indexSetWithIndex:0] options:NSEnumerationConcurrent usingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {
}];
//按顺便遍历获取相册中所有的资源，index代表资源的索引，stop赋值为false时，会停止遍历
[group enumerateAssetsUsingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {
}];
//按顺便遍历获取相册中所有的资源，遍历顺序可以是先序或倒序，index代表资源的索引，stop赋值为false时，会停止遍历
[group enumerateAssetsWithOptions:NSEnumerationReverse usingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {
}];
} failureBlock:^(NSError *error) {
}];
}
} failureBlock:^(NSError *error) {
}];
}];
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，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。
//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];
左侧为等比缩略图效果，右侧为poster效果的缩略图
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);
}];
//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]);
ALAssetsLibrary被封装在 框架中。所以，我们在使用时，需要引入该框架。
需添加AssetsLibrary.framework
然后引入
#import <AssetsLibrary/ALAsset.h>
#import <AssetsLibrary/ALAssetsLibrary.h>
#import <AssetsLibrary/ALAssetsGroup.h>
#import <AssetsLibrary/ALAssetRepresentation.h>
_library = [[ALAssetsLibrary alloc]init];
//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
[NSThread sleepForTimeInterval:0.5];
//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) {
}];
//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);
}];
ALAssetsGroup类是系统用于映射相册资源中的每个相册，可以通过该类获取相册中的资源文件，并且能向相册中添加资源文件
//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);
//通过ALAssetsLibrary迭代取出所有相册
[_library enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
NSString* groupname = [group valueForProperty:ALAssetsGroupPropertyName];
//如果相册的名称是test的时候，对其进行操作
if ([groupname isEqualToString:@"test"]) {
//设置相册组的筛选条件，ALAssetsFilter类表示筛选条件，allPhotos代表相册只包含相片，allVideos代表只包含视频，allAssets代表包含所有资源
[group setAssetsFilter:[ALAssetsFilter allPhotos]];
//通过刚保存的照片的url，把保存到默认相册的照片也保存到test相册中
[_library assetForURL:assetURL resultBlock:^(ALAsset *asset) {
//添加资源到指定的相册
[group addAsset:asset];
//获取相册中一共的资源数量
int count = [group numberOfAssets];
NSLog(@"count:%d",count);
dispatch_queue_t main = dispatch_get_main_queue();
dispatch_async(main, ^{
//获取相册的封面图片
CGImageRef poster = [group posterImage];
[imageView setImage:[UIImage imageWithCGImage:poster]];
});
//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]);
//按遍历顺序获取指定索引的资源，遍历顺序可以是先序或倒序
/*
enum {
NSEnumerationConcurrent = (1UL << 0),
NSEnumerationReverse = (1UL << 1),
};
typedef NSUInteger NSEnumerationOptions;
*/
[group enumerateAssetsAtIndexes:[NSIndexSet indexSetWithIndex:0] options:NSEnumerationConcurrent usingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {
}];
//按顺便遍历获取相册中所有的资源，index代表资源的索引，stop赋值为false时，会停止遍历
[group enumerateAssetsUsingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {
}];
//按顺便遍历获取相册中所有的资源，遍历顺序可以是先序或倒序，index代表资源的索引，stop赋值为false时，会停止遍历
[group enumerateAssetsWithOptions:NSEnumerationReverse usingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {
}];
} failureBlock:^(NSError *error) {
}];
}
} failureBlock:^(NSError *error) {
}];
}];
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，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。
//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];
左侧为等比缩略图效果，右侧为poster效果的缩略图
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);
}];
//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]);
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