CGImageMetadata.swift

import UIKit

import MobileCoreServices
import ImageIO

let sourceOptions: [String: AnyObject] = [kCGImageSourceTypeIdentifierHint as String: kUTTypeJPEG]
let cfSourceOptions = sourceOptions as CFDictionary

let image = UIImage(named: "input.jpg")!
let data = UIImageJPEGRepresentation(image, 1.0)
let source: CGImageSource = CGImageSourceCreateWithData(data as! CFData, cfSourceOptions)!

let filepath = NSTemporaryDirectory().appending("out.jpg")

print("Output file:")
print(filepath)

let fileURL: URL = URL(fileURLWithPath: filepath)
let destination: CGImageDestination = CGImageDestinationCreateWithURL(fileURL as CFURL, kUTTypeJPEG, 1, nil)!

var makeTag = CGImageMetadataTagCreate(
    kCGImageMetadataNamespaceTIFF, kCGImageMetadataPrefixTIFF, kCGImagePropertyTIFFMake, .string, "Make" as CFString
)!

var modelTag = CGImageMetadataTagCreate(
    kCGImageMetadataNamespaceTIFF, kCGImageMetadataPrefixTIFF, kCGImagePropertyTIFFModel, .string, "Model" as CFString
)!

var metaDatas = CGImageMetadataCreateMutable()

var tagPath = "tiff:Make" as CFString
var result = CGImageMetadataSetTagWithPath(metaDatas, nil, tagPath, makeTag)

tagPath = "tiff:Model" as CFString
result = CGImageMetadataSetTagWithPath(metaDatas, nil, tagPath, modelTag)

let destOptions: [String: AnyObject] = [
    kCGImageDestinationMergeMetadata as String: NSNumber(value: 1),
    kCGImageDestinationMetadata as String: metaDatas
]

let cfDestOptions = destOptions as CFDictionary

var error: Unmanaged<CFError>?
var errorPtr: UnsafeMutablePointer<CFError>
withUnsafeMutablePointer(to: &error, { ptr in
    result = CGImageDestinationCopyImageSource(destination, source, cfDestOptions, ptr)
    print(String(format: "Write image to file result: %@", result ? "Success" : "Failed"))
    print(String(format: "With error: %@", error.debugDescription))
})

let writeResult = CGImageDestinationFinalize(destination)

// This is false, and you may see an error like:
// " ImageIO: finalize:2031: not allowed for image destination that was updated with CGImageDestinationCopyImageSource "
// But, in practice, it works. The file is there and the metadata is correct.
print(writeResult)

@maurymarkowitz no idea about errorPtr I ended up not having that line in production. Thanks for the tips too!