Combine two images with CGAffineTransform - swift

Question

I am using the new Apple Vision API's VNImageTranslationAlignmentObservation to get a CGAffineTransform returned. The idea is that you pass it two images that can be merged together and it returns the CGAffineTransform so that you can do so. I have managed to get the code working so that i get a CGAffineTransform returned but after a lot of reading im at a loss as how i can merge two images with the information.
My code is here:
import UIKit
import Vision
class ImageTranslation {
let referenceImage: CGImage!
let floatingImage: CGImage!
let imageTranslationRequest: VNTranslationalImageRegistrationRequest!
init(referenceImage: CGImage, floatingImage: CGImage) {
self.referenceImage = referenceImage
self.floatingImage = floatingImage
self.imageTranslationRequest = VNTranslationalImageRegistrationRequest(targetedCGImage: floatingImage, completionHandler: nil)
}
func handleImageTranslationRequest() -> UIImage {
var alignmentTransform: CGAffineTransform!
let vnImage = VNSequenceRequestHandler()
try? vnImage.perform([imageTranslationRequest], on: referenceImage)
if let results = imageTranslationRequest.results as? [VNImageTranslationAlignmentObservation] {
print("Image Transformations found \(results.count)")
results.forEach { result in
alignmentTransform = result.alignmentTransform
print(alignmentTransform)
}
}
return applyTransformation(alignmentTransform)
}
private func applyTransformation(_ transform: CGAffineTransform) -> UIImage {
let image = UIImage(cgImage: referenceImage)
return image
}
}
The printed transform i get is like so CGAffineTransform(a: 1.0, b: 0.0, c: 0.0, d: 1.0, tx: 672.0, ty: 894.0)
How can i apply this two the two images passed in?

Answer 1

I've been playing with some examples (portrait images only but should work with landscape also) and this has worked:
func mergeImages(first image1:UIImage, second image2:UIImage, transformation: CGAffineTransform) -> UIImage {
let size = CGSize(width: image1.size.width + image2.size.width - (image2.size.width - transformation.tx), height: image1.size.height + image2.size.height - (image2.size.height - transformation.ty))
let renderer = UIGraphicsImageRenderer(size: size)
return renderer.image { context in
let pointImg2 = CGPoint.zero.applying(transformation)
image2.draw(at: pointImg2)
let pointImg1 = CGPoint.zero
image1.draw(at: pointImg1)
}
}
Let me know if it isn't working (upload your sample images if you can) and I'll fix it.