In the example https://developer.apple.com/documentation/imageio/writing-spatial-photos, we see that for each image encoded with the photo we include the following information:
kCGImagePropertyGroups: [
kCGImagePropertyGroupIndex: 0,
kCGImagePropertyGroupType: kCGImagePropertyGroupTypeStereoPair,
(isLeft ? kCGImagePropertyGroupImageIsLeftImage : kCGImagePropertyGroupImageIsRightImage): true,
kCGImagePropertyGroupImageDisparityAdjustment: encodedDisparityAdjustment
],
Which will identify which image is left, and which is right, also information about group type = stereo pair.
Now, how do you read those back?
I tried to implement a reading simply with CGImageSourceCopyPropertiesAtIndex, and that did not work, getting back "No property groups found."
func tryToReadThose() {
guard
let imageData = try? Data(contentsOf: outputImageURL),
let source = CGImageSourceCreateWithData(imageData as NSData, nil)
else {
print("cannot read")
return
}
for i in 0..<CGImageSourceGetCount(source) {
guard let imageProperties = CGImageSourceCopyPropertiesAtIndex(source, i, nil) as? [String: Any] else {
print("cannot read options")
continue
}
if let propertyGroups = imageProperties[String(kCGImagePropertyGroups)] as? [Any] {
// Process the property groups as needed
print(propertyGroups)
} else {
print("No property groups found.")
}
//print(imageProperties)
}
}
I assume maybe CGImageSourceCopyPropertiesAtIndex expects something as a 3rd parameter. But in the https://developer.apple.com/documentation/imageio/cgimagesource "Specifying the Read Options" I don't see anything related to that.
You're on the right track. The next steps are:
- Find the group that contains the stereo pair.
- Extract the left and right index from that group.
- Use the indexes to create the left and right images.
let imageSource = CGImageSourceCreateWithURL(url as CFURL, nil),
let cfProps = CGImageSourceCopyProperties(imageSource, nil) {
let props = cfProps as Dictionary
if let groups = props[kCGImagePropertyGroups] as? [[CFString:Any]] {
let stereoGroup = groups.first(where: {
let groupType = $0[kCGImagePropertyGroupType] as! CFString
return groupType == kCGImagePropertyGroupTypeStereoPair
})
if let stereoGroup,
let leftIdx = stereoGroup[kCGImagePropertyGroupImageIndexLeft] as? Int,
let rightIdx = stereoGroup[ kCGImagePropertyGroupImageIndexRight] as? Int,
let leftImage = CGImageSourceCreateImageAtIndex(imageSource, leftIdx, nil),
let rightImage = CGImageSourceCreateImageAtIndex(imageSource, rightIdx, nil) {
// Do things with the left and right images!
}
}
