VNFaceObservation extension for calculate the overall bounding box that contains face observation bounding boxes.

VNFaceObservation.extension.swift

extension VNFaceObservation {
    
    static func overAllBoundingBoxFrom(boundingBoxes: [CGRect], tolerance: CGFloat) -> CGRect {
        
        /// Sort Max X coordinates
        let originXCoordinates = boundingBoxes.map { $0.minX }
        /// Sort Max Y coordinates
        let originYCoordinates = boundingBoxes.map { $0.minY }
        /// Find overall minX
        guard let minOverallX = originXCoordinates.min() else { return CGRect.zero }
        /// Find overall minY
        guard let minOveralY = originYCoordinates.min() else { return CGRect.zero }
        /// Find overall maxX
        
        ///Find originY + height = rect.maxY
        let maxYFromRects = boundingBoxes.map { $0.maxY }
        
        ///Find originX + width = rect.maxX
        let maxXFromRects = boundingBoxes.map { $0.maxX }
        
        /// Find overall maxX
        guard let maxOverallX = maxXFromRects.max() else { return CGRect.zero }
        /// Find overall maxY
        guard let maxOverallY = maxYFromRects.max() else { return CGRect.zero }

        let finalWidth = maxOverallX - minOverallX + tolerance * 2
        let finalHeight = maxOverallY - minOveralY + tolerance * 2
        let overallOriginY = minOveralY - tolerance
        let overallOriginX = minOverallX - tolerance
        
        return CGRect(x: overallOriginX, y: overallOriginY, width: finalWidth, height: finalHeight)
    }
}