Extracting HDR Gain Map from iOS 14.1+ (iPhone 12+) photos

import UIKit import MobileCoreServices.UTCoreTypes

if #available(iOS 14.1, *) { let input = Bundle.main.url(forResource: "IMG_0037", withExtension: "HEIC")! let output = FileManager().temporaryDirectory.appendingPathComponent("IMG_0037.GAIN_MAP.BMP") let source = CGImageSourceCreateWithURL(input as CFURL, nil)!

// urn:com:apple:photo:2020:aux:hdrgainmap
let dataInfo = CGImageSourceCopyAuxiliaryDataInfoAtIndex(source, 0, kCGImageAuxiliaryDataTypeHDRGainMap)! as Dictionary
let data = dataInfo[kCGImageAuxiliaryDataInfoData] as! Data
let description = dataInfo[kCGImageAuxiliaryDataInfoDataDescription]! as! [String: Int]
let size = CGSize(width: description["Width"]!, height: description["Height"]!)

let ciImage = CIImage(bitmapData: data, bytesPerRow: description["BytesPerRow"]!, size: size, format: .L8, colorSpace: nil)
let cgImage = CIContext().createCGImage(ciImage, from: CGRect(origin: CGPoint(x: 0, y: 0), size: size))!

let destRef = CGImageDestinationCreateWithURL(output as CFURL, kUTTypeBMP, 1, nil)!
CGImageDestinationAddImage(destRef, cgImage, [:] as CFDictionary)
CGImageDestinationFinalize(destRef)

print(output)

}