An extension for UIImageView that provides useful tools for handling the scaled size of the image, the padding added by the UIImageView and X/Y coordinate mapping.

UIImageViewAdditions.swift

//
//  UIImageView Additions
//
//  Created by Nathan Fiscaletti on 11/12/18.
//  Copyright © 2018 Nathan Fiscaletti. All rights reserved.
//
//  An extension for UIImageView that provides useful tools for
//  handling the scaled size of the image, the padding added by
//  the UIImageView and X/Y coordinate mapping.
//
extension UIImageView {
    /// Retrieve the scaled size of the image within this ImageView.
    ///
    /// - Returns:
    ///     - A CGRect representing the size of the image after scaling or nil if no image is set.
    ///
    func getScaledImageSize() -> CGRect? {
        if let image = self.image {
            return AVMakeRect(aspectRatio: image.size, insideRect: self.frame);
        }

        return nil;
    }
    
    /// Retrieve the size of the image including the padding added by the UIImageView.
    ///
    /// - Returns:
    ///    - A CGRect reresenting the size including the padding.
    ///
    func getScaledImageSizeWithPadding() -> CGRect? {
        if let size = getScaledImageSize(),
           let paddingTop = getPaddingTop(),
           let paddingBottom = getPaddingBottom(),
           let paddingLeft = getPaddingLeft(),
           let paddingRight = getPaddingRight() {
            
            return CGRect(x: size.minX + paddingLeft, y: size.minY + paddingTop, width: size.width + paddingLeft + paddingRight, height: size.height + paddingTop + paddingBottom);
            
        }
        
        return nil;
    }
    
    /// Retrieve the top padding between the scaled image in this ImageView and
    /// the ImageView itself.
    ///
    /// - Returns:
    ///    - A CGFloat representing the padding, or nil if no image is set.
    ///
    func getPaddingTop() -> CGFloat? {
        if let size = self.getScaledImageSize() {
            switch self.contentMode {
            case .bottom, .bottomLeft, .bottomRight :
                return self.frame.height - size.height;
            case .top, .topLeft, .topRight :
                return 0;
            default:
                return (self.frame.height - size.height) / 2;
            }
        }
        
        return nil;
    }
    
    /// Retrieve the bottom padding between the scaled image in this ImageView
    /// and the ImageView itself.
    ///
    /// - Returns:
    ///     - A CGFloat representing the padding, or nil if no image is set.
    ///
    func getPaddingBottom() -> CGFloat? {
        if let size = self.getScaledImageSize() {
            switch self.contentMode {
            case .bottom, .bottomLeft, .bottomRight :
                return 0;
            case .top, .topLeft, .topRight :
                return self.frame.height - size.height;
            default:
                return (self.frame.height - size.height) / 2;
            }
        }
        
        return nil;
    }
    
    /// Retrieve the left padding between the scaled image in this ImageView
    /// and the ImageView itself.
    ///
    /// - Returns:
    ///    - A CGFloat representing the padding, or nil if no image is set.
    ///
    func getPaddingLeft() -> CGFloat? {
        if let size = self.getScaledImageSize() {
            switch self.contentMode {
            case .left, .bottomLeft, .topLeft :
                return 0;
            case .right, .bottomRight, .topRight :
                return self.frame.width - size.width;
            default :
                if (self.frame.width - size.width) > 0 {
                    return (self.frame.width - size.width) / 2;
                } else {
                    return 0;
                }
            }
        }
        
        return nil;
    }
    
    /// Retrieve the right padding between the scaled image in this ImageView
    /// and the ImageView itself.
    ///
    /// - Returns:
    ///    - A CGFloat representing the padding, or nil if no image is set.
    ///
    func getPaddingRight() -> CGFloat? {
        if let size = self.getScaledImageSize() {
            switch self.contentMode {
            case .left, .bottomLeft, .topLeft :
                return self.frame.width - size.width;
            case .right, .bottomRight, .topRight :
                return 0;
            default :
                if (self.frame.width - size.width) > 0 {
                    return (self.frame.width - size.width) / 2;
                } else {
                    return 0;
                }
            }
        }
        
        return nil;
    }
    
    /// Retrieve the coordinate from the base image scaled to the new scaled image.
    ///
    /// - Parameters:
    ///     - x: The X coordinate.
    ///     - y: The Y coordinate.
    ///     - multiplier: The multiplier to use (default is 100).
    /// - Returns:
    ///     - A CGPoint representing the value, or nil if no image is set.
    ///
    func getScaledCoordinate(forX x: CGFloat, andY y: CGFloat, multiplier:CGFloat = 100.0) -> CGPoint? {
        if let size = self.getScaledImageSize() {
            let xCoordSize = size.width / multiplier;
            let yCoordSize = size.height / multiplier;
            
            return CGPoint(x: x * xCoordSize, y: y * yCoordSize);
        }
        
        return nil;
    }
    
    /// Retrieve the coordinate from the base image scaled to the new scaled image,
    /// including the padding added by the UIImageView.
    ///
    /// - Parameters:
    ///     - x: The X coordinate.
    ///     - y: The Y coordinate.
    ///     - multiplier: The multiplier to use (default is 100).
    /// - Returns:
    ///     - A CGPoint representing the value, or nil if no image is set.
    ///
    func getScaledCoordinateWithPadding(forX x: CGFloat, andY y: CGFloat, multiplier:CGFloat = 100.0) -> CGPoint? {
        if let point = self.getScaledCoordinate(forX: x, andY: y, multiplier: multiplier),
           let paddingTop = self.getPaddingTop(),
           let paddingLeft = self.getPaddingLeft() {
            return CGPoint(x: point.x + paddingLeft, y: point.y + paddingTop);
        }
        
        return nil;
    }
}