Is it possible to use ARReferenceImage objects created programatically from the images on iOS 11.3.1

Question

Created Jun ’20

Replies 2

Boosts 0

Participants 2

The images that I want to track downloaded from the web service and stored locally. I'm creating the ARImageReference objects from them using the following code:

Code Block guard
		let image = UIImage(contentsOfFile: imageLocalPath),
		let cgImage = image.cgImage
else {
		return nil
}
return ARReferenceImage(cgImage, orientation: .up, physicalWidth: 0.12)

The session configured depending on the current iOS version since ARImageTrackingConfiguration not available for iOS 11:

Code Block private lazy var configuration: ARConfiguration = {
		if #available(iOS 12.0, *),
				ARImageTrackingConfiguration.isSupported {
				return ARImageTrackingConfiguration()
		}
		return ARWorldTrackingConfiguration()
}()
if #available(iOS 12.0, *),
		let imagesTrackingConfig = configuration as? ARImageTrackingConfiguration {
		imagesTrackingConfig.trackingImages = referenceImages
} else if let worldTrackingConfig = configuration as? ARWorldTrackingConfiguration {
		worldTrackingConfig.detectionImages = referenceImages
}
session.run(configuration, options: [.resetTracking, .removeExistingAnchors])

The code above works fine for iOS 12 and 13 even if I use ARWorldTrackingConfiguration. Images correctly detected by the ARKit. But when I try to run it on iOS 11.3.1, the app immediately crashes with the following error:

Assert: /BuildRoot/Library/Caches/com.apple.xbs/Sources/AppleCV3D/AppleCV3D-1.13.11/library/VIO/OdometryEngine/src/FrameDownsampleNode/FrameDownsampler.cpp, 62: std::abs(staticcast(aspect1) - staticcast(srcframe.image.width * outputframeheight)) < maxslack (lldb)

Is it possible that the dynamic markers creation programmatically is not available for the iOS version below 12.0 or am I doing something wrong? Unfortunately, I wasn't able to find any information regarding the specific versions. Thank you.

Answered by liubonexo in 616309022

Thanks for pointing me in the right direction.

I managed to solve the issue a few days ago by redrawing the images that come from the API.
By checking the original images CGImage size, I discovered that they have the same sizes as the UIImage.
But they must be scaled, for example, on iPhone 8 plus in case if the images with the size 180 x 240, the output cgImage must be 540 x 720, with x3 scale.
By using the correctly scaled CGImage object for the creation of the ARReferenceImage, I got rid of the crash, and the detection works fine now on iOS 11.3.1 as well.

Boost

Answer 1

Vision Pro Engineer OP

Apple

Jun ’20

The error indicates that the image which you are trying to load has an unsupported (too large) aspect ratio. Have you tried loading other images with varying aspect ratios?

1

Answer 2

liubonexo OP

Jun ’20

Accepted Answer

Thanks for pointing me in the right direction.

I managed to solve the issue a few days ago by redrawing the images that come from the API.
By checking the original images CGImage size, I discovered that they have the same sizes as the UIImage.
But they must be scaled, for example, on iPhone 8 plus in case if the images with the size 180 x 240, the output cgImage must be 540 x 720, with x3 scale.
By using the correctly scaled CGImage object for the creation of the ARReferenceImage, I got rid of the crash, and the detection works fine now on iOS 11.3.1 as well.

1