ios – 如何从ALAsset对象获取全景图

概述我们有大约2k个对象,它们是ALAsset类的实例,我们需要知道哪些文件是全景图像. 我们试图从ALAsset实例获取CG ImageRef并检查宽度/高度比. ALAsset *alasset = ...CFImageRef = alasset.thumbnail; // return square thumbnail and not suitable for meCFImageRef = 我们有大约2k个对象,它们是ALAsset类的实例,我们需要知道哪些文件是全景图像.
我们试图从ALAsset实例获取CG ImageRef并检查宽度/高度比.

ALAsset *alasset = ...CFImageRef = alasset.thumbnail; // return square thumbnail and not suitable for meCFImageRef = alasset.aspectRationthumbnail; //return aspect ration thumbnail,but very slowly

它不适合我们,因为它适用于许多文件.

此外,我们尝试从defaultRepresentation获取元数据并检查图像EXIF,但它工作缓慢.

NSDictionary *dictionary = [alasset defaultRepresentation] Metadata]; //very slowly to

有没有办法让它变得更好？

谢谢

解决方法 最后,我发现了ALAsset的这个解决方案：

ALAssetsLibrary *AssetsLibrary = ...;NSOperation *queue = [NSoperationQueue alloc] init];static Nsstring * const kAssetQueue@R_404_6889@ = ...;static NSUInteger const kAssetConcurrentoperationCount = ...; //I use 5 queue.maxConcurrentoperationCount = kAssetConcurrentoperationCount;queue.@R_404_6889@ = kAssetQueue@R_404_6889@;dispatch_async(dispatch_get_main_queue(),^{  [AssetsLibrary enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:^(ALAssetsGroup *group,BOol *stop) {    /*You must check the group is not nil */    if (!group)      return;    /*Then you need to select group where you will search panoramas: for iPhone-Simulator it's @"Saved Photos" and "Camera Roll" for  iPhone. It's actuality only for iOS 7 or early. */    static Nsstring * const kAssetGroup@R_404_6889@ = ...;    if ([[group valueForProperty:ALAssetsGroupProperty@R_404_6889@] kAssetGroup@R_404_6889@]) {      [group enumerateAssetsUsingBlock:^(ALAsset *asset,NSUInteger index,BOol *stop) {        if (!asset)          return;        [queue addOperationWithBlock:^{         //I use @autoreleasepool for instant memory release,after I find panoramas asset url          @autoreleasepool {            ALAssetRepresentation *defaultRepresentation = asset.defaultRepresentation;            if ([defaultRepresentation.UTI isEqualToString:@"public.jpeg"]) {              NSDictionary *Metadata = defaultRepresentation.Metadata;              if (!Metadata)                 return;              if (Metadata[@"PixelWIDth"] && Metadata[@"PixelHeight"]) {                NSInteger pixelWIDth = [Metadata[@"PixelWIDth"] integerValue];                NSInteger pixelHeight = [Metadata[@"PixelHeight"] integerValue];                static NSUInteger const kSIDesRelationshipConstant = ...; //I use 2                static NSUInteger const kMinimalPanoramaHeight = ...; //I use 600                if (pixelHeight >= kMinimalPanoramaHeight && pixelWIDth/pixelHeight >= kSIDesRelationshipConstant) {/*So,that is panorama.*/}             }        }];      }];    }  } failureBlock:^(NSError *error) {      //Some failing action,you kNow.  }];};

那是.所以,我认为这不是最好的解决方案.但是,今天我没有找到更好的.

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