Crop part of image within width x height bounds in SwiftUI

Question

I'm building a Mac OS app in SwiftUI. I have a use case where I must crop part of the image (which is a screenshot) and ensure the cropped part is at least 320x240 and match the aspect ratio if it exceeds.

I have below code so far:

func fitImageInRect(_ original: NSImage, rect: CGRect) -> NSImage {
    var originalRect = CGRect(x: 0, y: 0, width: original.size.width, height: original.size.height)
    var width = 0.0, height = 0.0
    if rect.width > rect.height {
        width = rect.width
        if width > 320 {
            let ratio = width / 320
            height = 240 * ratio
        } else {
            width = 320
            height = 240
        }
    } else {
        height = rect.height
        if height > 240 {
            let ratio = height / 240
            width = 320 * ratio
        } else {
            width = 320
            height = 240
        }
    }

    var originX = rect.origin.x
    var originY = rect.origin.y
    
    if originX > (originalRect.width - 320) {
        originX = originalRect.width - 320
    }
    
    if originY > (originalRect.height - 240) {
        originY = originalRect.height - 240
    }

    let thumbnailRect = CGRect(x: Int(originX), y: Int(originY), width: Int(width), height: Int(height))

    guard let ref = original.cgImage(forProposedRect: &originalRect, context: nil, hints: nil) else { return original }
    let cropped = ref.cropping(to: thumbnailRect)

    return NSImage(cgImage: cropped!, size: NSSize(width: width, height: height))
}

The goal is as follows:

1. If the rect size is 150x50, then the cropped photo be 320x240 with rect at center of it.
2. If the rect size is 640x50, then the cropped photo be 640x480 with rect at center of it.

But somehow, the code is behaving otherwise. The final output is seemingly from a vertically flipped thumbnailRect and I can't figure out why.