Following WWDC 2023 "Support HDR images in your app", I'm trying to save 48-megapixel ProRAWs (taken on an iPhone 14 Pro Max) as HDR HEICs to the Photo Library. After processing the ProRAW file using CIRAWFilter, whether I use CIContext.heif10Representation() or convert to a CGImage, then UIImage, and use UIImage.heicData(), I get photos that behave oddly in the Photo Library. They appear too dark, and visibly brighten when first viewed, but more problematic is that the photos brighten a great deal more when you edit them with the Photos editor. This is the behavior when using the itur_2100_PQ color space, but itur_2100_HLG behaves similarly, except that it gets dramatically darker when edited. This behavior occurs whether CIRAWFilter.extendedDynamicRangeAmount is set to 0.0, or 2.0, or not set at all.
So what am I doing wrong? Here is a minimal iOS app -- well, just the ContentView -- that demonstrates the issue. You also need a .dng ProRAW file included in the project directory named test.dng. I'd love to include such a file, but I can't.
Be prepared for a multi-second wait when you save the photo.
import SwiftUI
import Photos
struct ContentView: View {
let context = CIContext()
let hdrColorSpace = CGColorSpace(name: CGColorSpace.itur_2100_PQ)!
var body: some View {
VStack(spacing: 100) {
Button("Save Photo From CGImage/UIImage") {
savePhotoFromUIImage()
}
Button("Save Photo From CIImage") {
savePhotoDirectFromCIImage()
}
}.padding(60)
}
//convert RAW with CIRAWFilter to CIImage, then convert to CGImage, then UIImage, then HEIF
private func savePhotoFromUIImage() {
if let ciImage = processRAW(url: Bundle.main.url(forResource:"test", withExtension: "dng")!) {
guard let outputCGImage = context.createCGImage(ciImage, from: ciImage.extent, format: .RGB10, colorSpace: hdrColorSpace) else { return }
let uiImage = UIImage(cgImage: outputCGImage)
if let heicData = uiImage.heicData() {
saveHEIFPhotoToLibrary(imageData: heicData)
} else {
print("Failed to convert UIImage to HEIC")
}
}
}
//convert RAW with CIRAWFilter to CIImage, then to HEIF
private func savePhotoDirectFromCIImage() {
if let ciImage = processRAW(url: Bundle.main.url(forResource:"test", withExtension: "dng")!) {
do {
let heif = try context.heif10Representation(of: ciImage, colorSpace: hdrColorSpace)
saveHEIFPhotoToLibrary(imageData: heif)
} catch {
print("Failed to get HEIF representation from CIContext")
}
}
}
private func processRAW(url: URL) -> CIImage? {
guard let coreRawFilter = CIRAWFilter(imageURL: url) else { return nil }
coreRawFilter.extendedDynamicRangeAmount = 2.0 //the issue persists whether this is not set, or set to 0, or set to, say, 2.0
guard let ciImage = coreRawFilter.outputImage else { return nil }
return ciImage
}
private func saveHEIFPhotoToLibrary(imageData: Data) {
PHPhotoLibrary.shared().performChanges({
let creationRequest = PHAssetCreationRequest.forAsset()
let options = PHAssetResourceCreationOptions()
creationRequest.addResource(with: .photo, data: imageData, options: options)
}) { success, error in
if let error = error {
print("Error saving photo: \(error.localizedDescription)")
} else {
print("Photo saved.")
}
}
}
}