gistfile1.txt

 NSString *filePathInAssetsFolder = [assetURL.path stringByReplacingOccurrencesOfString:self.managedAssetFolderURL.path withString:@""];
    NSString *resolution = @"1x";
   
    //strip out the resolution from the filename and use it to populate the resolutions array
    NSRange lastResolutionOccurrence = [filePathInAssetsFolder rangeOfString:@"@" options:NSBackwardsSearch]; //in case they have the resolution in filename more than once
    if (lastResolutionOccurrence.location != NSNotFound) {
        NSString *extension = [filePathInAssetsFolder pathExtension];
        NSString *pathUpToResolutionString = [filePathInAssetsFolder substringToIndex:lastResolutionOccurrence.location];
       
        NSRange extensionLocation = [filePathInAssetsFolder rangeOfString:@"." options:NSBackwardsSearch];
        if (extensionLocation.location != NSNotFound){
            NSRange resolutionRange = NSMakeRange(lastResolutionOccurrence.location, extensionLocation.location - lastResolutionOccurrence.location);
            resolution = [filePathInAssetsFolder substringWithRange:resolutionRange];
        }
        
        filePathInAssetsFolder = [pathUpToResolutionString stringByAppendingPathExtension:extension];
    } 
    
    NSLog(@"File path = %@", filePathInAssetsFolder);