iOS 使用ALAssetsLibrary在裝置中的所有照片信息(建立時間,拍攝位置,尺寸 等)

有專案內容是要抓到照片裡的照片資訊,因此做出一些整理.

ALAssetsLibrary 提供了訪問iOS裝置下照片應用下所有照片和影片的接口.



從 ALAssetsLibrary 中可讀取所有的相簿資料,即 ALAssetsGroup 對象列表；
從每個 ALAssetsGroup 中可獲取到其中包含的照片或影片列表,即 ALAsset 對象列表.
其層次關係為 ALAssetsLibrary -> ALAssetsGroup -> ALAsset -> ALAssetRepresentation.
1. 每個 ALAsset 可能有多個representations表示, 即ALAssetRepresentation 對象:
2. 使用其defaultRepresentation 方法可獲得其默認representations，
3. 使用[asset valueForProperty: ALAssetPropertyRepresentations ]可獲取其所有representations的 UTI 數組。
4. 從ALAsset對象可獲取縮略圖 thumbnail 或 aspectRatioThumbnail ；
5. 從 ALAssetRepresentation 對象可獲取全尺寸圖片(fullResolutionImage), 全螢幕圖片(fullScreenImage)及圖片的各種屬性: orientation, dimensions, scale, url, metadata等。

範例程式碼如下：
#import <AssetsLibrary/AssetsLibrary.h> UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(10, 64, self.view.frame.size.width - 20, self.view.frame.size.height - 128)]; [self.view addSubview:imageView]; ALAssetsLibrary *assetsLibrary = [[ALAssetsLibrary alloc] init]; // asynchronous [assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:^(ALAssetsGroup *group, BOOL *stop) { if (group) { NSLog(@"group : %@", group); // ㄊ UIImage *cover = [[UIImage alloc] initWithCGImage:[group posterImage]]; [group enumerateAssetsUsingBlock:^(ALAsset *asset, NSUInteger index, BOOL *stop) { if (asset) { NSLog(@"\nasset : %@", asset); NSLog(@"ALAssetPropertyAssetURL : %@", [asset valueForProperty:ALAssetPropertyAssetURL]); UIImage *image = [[UIImage alloc] initWithCGImage:[[asset defaultRepresentation] fullScreenImage]]; // url NSString *url = [[[asset defaultRepresentation] url] absoluteString]; NSLog(@"url : %@", url); // 縮圖 UIImage *thumbnail = [[UIImage alloc] initWithCGImage:[asset thumbnail]]; UIImage *aspectRatioThumbnail = [[UIImage alloc] initWithCGImage:[asset aspectRatioThumbnail]]; // 每個ALAsset都可能有多個representation表示, 即ALAssetRepresentation對象. NSArray *utiArrays = [NSArray arrayWithObject:[asset valueForProperty:ALAssetPropertyRepresentations]]; NSLog(@"utiArrays : %@", utiArrays); // 全尺寸圖 UIImage *fullResolutionImage = [UIImage imageWithCGImage:[[asset defaultRepresentation] fullResolutionImage]]; // 全螢幕圖 UIImage *fullScreenImage = [UIImage imageWithCGImage:[[asset defaultRepresentation] fullScreenImage]]; imageView.image = fullResolutionImage; // 建立時間 NSString *createTime = (NSString *)[asset valueForProperty:ALAssetPropertyDate]; NSLog(@"createTime : %@", createTime); // 拍攝位置 NSString *createLocation = (NSString *)[asset valueForProperty:ALAssetPropertyLocation]; NSLog(@"createLocation : %@", createLocation); // 尺寸 CGSize dimensions = [[asset defaultRepresentation] dimensions]; NSLog(@"dimensions : %f - %f", dimensions.width, dimensions.height); } }]; } } failureBlock:^(NSError *error) { NSLog(@"%@", error); }];