ios, swift, image metadata, XMP, DJI Drones

Question

Created Feb ’23

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I'm writing an iOS Swift app to fetch metadata from DJI drone images. I'm trying to access the Xmp.drone-dji.X metadata. The iOS/Swift CGImageSource and CGImageMetadata libraries/classes get almost all of the metadata out of the image but not the Xmp.drone-dji. When I get a list of tags, those tag/values are not listed. I know the tags/data are in the images because I've examined the images using exif, exiv2, etc.

Any suggestions?

Here is the code I'm using so far:

result.itemProvider.loadDataRepresentation(forTypeIdentifier: UTType.image.identifier) { data, err in if let data = data {

    let src = CGImageSourceCreateWithData(data as CFData,nil)!
    let md = CGImageSourceCopyPropertiesAtIndex(src,0,nil) as! NSDictionary
    let md2 = CGImageSourceCopyMetadataAtIndex(src,0,nil)
}

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Answer 1

rdkapple OP

Feb ’23

Accepted Answer

So, after a lot of searching, trial and error, I have found an answer.

I was not able to get any of the CGImage swift libraries to extract this info for me.

Adobe has a c++ library that parses xmp/xml data out of images and it purports to support iOS. I didnt want the hassle of building c++ on iOS, importing that into Xcode and then dealing with the fact that thrown errors do not propagate well from c++/objectiveC to Swift.

So, at a high level, I did the following:

get the bytes of the raw image as CFData or Data then cast to a String
then use String.range() to find beginning of XML/XMP data in image searching for substring "<?xpacket begin"
use String.range() to find end of XML/XMP data in image using substring ""
Extract the XML document out of image data String
Use Swift XMLParser class to parse the XML and then copying attributes and elements as necessary. I just simply added what I wanted to already existing Exif NSdictionary returned by CGImage classes.

Happy to answer questions on this approach. My code will eventually be uploaded to GitHub under OpenAthenaIOS project.

Bobby

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