How to access HDRGainMap from AVCapturePhoto

Question

Created Jan ’25

Replies 2

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Participants 2

Hey, I'm building a camera app and I want to use the captured HDRGainMap along side the photo to do some processing with a CIFilter chain. How can this be done? I can't find any documentation any where on this, only on how to access the HDRGainMap from an existing HEIC file, which I have done successfully. For this I'm doing something like the following:

 let gainmap = CGImageSourceCopyAuxiliaryDataInfoAtIndex(source, 0, kCGImageAuxiliaryDataTypeHDRGainMap)
let gainDict = NSDictionary(dictionary: gainmap)
let gainData = gainDict[kCGImageAuxiliaryDataInfoData] as? Data
let gainDescription = gainDict[kCGImageAuxiliaryDataInfoDataDescription]
let gainMeta = gainDict[kCGImageAuxiliaryDataInfoMetadata]

However I'm not sure what the approach is with a AVCapturePhoto output from a AVCaptureDevice.

Thanks!

Answered by DTS Engineer in 821329022

Hello @alexfoxdev,

Assuming there is an HDR gain map in the photo your captured, you can access it like this:

 // `photo` is an AVCapturePhoto
let data = photo.fileDataRepresentation()!
        
let gainMap = CIImage(data: data, options: [.auxiliaryHDRGainMap : true])
        
print(gainMap)

-- Greg

Boost

Answer 1

DTS Engineer OP

Apple

Jan ’25

Recommended

Hello @alexfoxdev,

Assuming there is an HDR gain map in the photo your captured, you can access it like this:

 // `photo` is an AVCapturePhoto
let data = photo.fileDataRepresentation()!
        
let gainMap = CIImage(data: data, options: [.auxiliaryHDRGainMap : true])
        
print(gainMap)

-- Greg

0

Answer 2

DTS Engineer OP

Apple

Jan ’25

Hello @alexfoxdev,

Make sure your capture device's activeFormat reports true for isHighestPhotoQualitySupported. (or use the ".photo" sessionPreset on the capture session).

-- Greg

0

	let gainmap = CGImageSourceCopyAuxiliaryDataInfoAtIndex(source, 0, kCGImageAuxiliaryDataTypeHDRGainMap)
	let gainDict = NSDictionary(dictionary: gainmap)
	let gainData = gainDict[kCGImageAuxiliaryDataInfoData] as? Data
	let gainDescription = gainDict[kCGImageAuxiliaryDataInfoDataDescription]
	let gainMeta = gainDict[kCGImageAuxiliaryDataInfoMetadata]

	// `photo` is an AVCapturePhoto
	let data = photo.fileDataRepresentation()!

	let gainMap = CIImage(data: data, options: [.auxiliaryHDRGainMap : true])

	print(gainMap)