iOS 8 Photos framework. Access photo metadata

Question

I\'m looking at replacing ALAssetsLibrary with Photos framework in my app.

I can retrieve photos, collections, and asset sources just fine (even write t

Answer 1

I thought I'd share some code to read the metadata using the ImageIO framework in conjunction with Photos framework. You must request the image data using a PHCachingImageManager.

@property (strong) PHCachingImageManager *imageManager;

Request the image and use it's data to create a metadata dictionary

-(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...
        }];

    }];
}

Convert NSData to metadata

-(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;
}

This has the overhead of grabbing the image, so it's not nearly as fast as enumerating your assets or collections, but it's something at least.