iOS 8照片框架.访问照片元数据

Question

我期待在更换ALAssetsLibrary与Photos框架在我的应用程序.

我可以很好地检索照片,集合和资源(甚至可以将它们写回来),但是看不到任何地方可以访问照片的元数据({Exif},{TIFF},{GPS}等字典,等等...).

ALAssetsLibrary有办法.UIImagePickerController有办法.Photos也必须有办法.

我看到它PHAsset有一个location属性可以用于GPS词典,但我希望访问所有的元数据,包括面部,方向,曝光,ISO和吨更多.

目前苹果处于测试阶段2.也许还有更多的API需要推出？

UPDATE

没有官方的方法只使用Photos API来做到这一点.

但是,您可以在下载图像数据后读取元数据.有几个方法来做到这一点使用两种PHImageManager或PHContentEditingInput.

该PHContentEditingInput方法需要较少的代码,不需要您导入ImageIO.我把它包装在PHAsset类别中.

Answer 1

如果您请求内容编辑输入,则可以将完整图像作为a CIImage,并且CIImage具有标题properties为包含图像元数据的字典的属性.

示例Swift代码:

let options = PHContentEditingInputRequestOptions()
options.networkAccessAllowed = true //download asset metadata from iCloud if needed

asset.requestContentEditingInputWithOptions(options) { (contentEditingInput: PHContentEditingInput?, _) -> Void in
    let fullImage = CIImage(contentsOfURL: contentEditingInput!.fullSizeImageURL)

    print(fullImage.properties)
}

示例Objective-C代码:

PHContentEditingInputRequestOptions *options = [[PHContentEditingInputRequestOptions alloc] init];
options.networkAccessAllowed = YES; //download asset metadata from iCloud if needed

[asset requestContentEditingInputWithOptions:options completionHandler:^(PHContentEditingInput *contentEditingInput, NSDictionary *info) {
    CIImage *fullImage = [CIImage imageWithContentsOfURL:contentEditingInput.fullSizeImageURL];

    NSLog(@"%@", fullImage.properties.description);
}];

您将获得所需的{Exif},{TIFF},{GPS}等词典.

Answer 2

我以为我会分享一些代码来使用ImageIO框架和Photos框架来阅读元数据.您必须使用PHCachingImageManager请求图像数据.

@property (strong) PHCachingImageManager *imageManager;

请求图像并使用它的数据来创建元数据字典

-(void)metadataReader{
    PHFetchResult *result = [PHAsset fetchAssetsInAssetCollection:self.myAssetCollection options:nil];
    [result enumerateObjectsAtIndexes:[NSIndexSet indexSetWithIndex:myIndex] options:NSEnumerationConcurrent usingBlock:^(PHAsset *asset, NSUInteger idx, BOOL *stop) {
        [self.imageManager requestImageDataForAsset:asset options:nil resultHandler:^(NSData *imageData, NSString *dataUTI, UIImageOrientation orientation, NSDictionary *info) {
            NSDictionary *metadata = [self metadataFromImageData:imageData];
                           NSLog(@"Metadata: %@", metadata.description);
            NSDictionary *gpsDictionary = metadata[(NSString*)kCGImagePropertyGPSDictionary];
            if(gpsDictionary){
                NSLog(@"GPS: %@", gpsDictionary.description);
            }
            NSDictionary *exifDictionary = metadata[(NSString*)kCGImagePropertyExifDictionary];
            if(exifDictionary){
                NSLog(@"EXIF: %@", exifDictionary.description);
            }

            UIImage *image = [UIImage imageWithData:imageData scale:[UIScreen mainScreen].scale];
            // assign image where ever you need...
        }];

    }];
}

将NSData转换为元数据

-(NSDictionary*)metadataFromImageData:(NSData*)imageData{
    CGImageSourceRef imageSource = CGImageSourceCreateWithData((__bridge CFDataRef)(imageData), NULL);
    if (imageSource) {
        NSDictionary *options = @{(NSString *)kCGImageSourceShouldCache : [NSNumber numberWithBool:NO]};
        CFDictionaryRef imageProperties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, (__bridge CFDictionaryRef)options);
        if (imageProperties) {
            NSDictionary *metadata = (__bridge NSDictionary *)imageProperties;
            CFRelease(imageProperties);
            CFRelease(imageSource);
            return metadata;
        }
        CFRelease(imageSource);
    }

    NSLog(@"Can't read metadata");
    return nil;
}

这具有抓取图像的开销,因此它不如枚举您的资产或集合那么快,但它至少是这样的.

Answer 3

我不喜欢 CIImage 解决方案，而是喜欢 ImageIO 解决方案：

func imageAndMetadataFromImageData(data: NSData)-> (UIImage?,[String: Any]?) {
    let options = [kCGImageSourceShouldCache as String: kCFBooleanFalse]
    if let imgSrc = CGImageSourceCreateWithData(data, options as CFDictionary) {
        let metadata = CGImageSourceCopyPropertiesAtIndex(imgSrc, 0, options as CFDictionary) as! [String: Any]
        //print(metadata)
        // let image = UIImage(cgImage: imgSrc as! CGImage)
        let image = UIImage(data: data as Data)
        return (image, metadata)
    }
    return (nil, nil)
}

下面是从 PHAseet 获取数据的代码

func getImageAndMeta(asset: PHAsset){
    let options = PHImageRequestOptions()
    options.isSynchronous = true
    options.resizeMode = .none
    options.isNetworkAccessAllowed = false
    options.version = .current
    var image: UIImage? = nil
    var meta:[String:Any]? = nil
    _ = PHCachingImageManager().requestImageData(for: asset, options: options) { (imageData, dataUTI, orientation, info) in
        if let data = imageData {
            (image, meta) = imageAndMetadataFromImageData(data: data as NSData)
            //image = UIImage(data: data)
        }
    }
    // here to return image and meta
}

Answer 4

PhotoKit将对元数据的访问限制为PHAsset的属性(location,creationDate,favorite,hidden,modificatonDate,pixelWidth,pixelHeight ......).原因(我怀疑)是由于引入了iCloud PhotoLibrary,图像可能不在设备上.因此,整个元数据不可用.只有这样,才能获得完整的EXIF/IPTC元数据将首先从iCloud中下载原始图像(如果不可用),然后使用的ImageIO以提取其元数据.

Answer 5

我发现并且对我有用的更好的解决方案是:

[[PHImageManager defaultManager] requestImageDataForAsset:photoAsset
                                                  options:reqOptions
                                            resultHandler:
         ^(NSData *imageData, NSString *dataUTI, UIImageOrientation orientation, NSDictionary *info) {
             CIImage* ciImage = [CIImage imageWithData:imageData];
             DLog(@"Metadata : %@", ciImage.properties);
         }];