Gifu/Source/Extensions/CGSize.swift

import Foundation
import UIKit
extension CGSize {
  /// Calculates the aspect ratio of the size.
  ///
  /// - returns: aspectRatio The aspect ratio of the size.
  var aspectRatio: CGFloat {
    if height == 0 { return 1 }
    return width / height
  }

  /// Finds a new size constrained by a size keeping the aspect ratio.
  ///
  /// - parameter size: The contraining size.
  /// - returns: size A new size that fits inside the contraining size with the same aspect ratio.
  func constrained(by size: CGSize) -> CGSize {
    let aspectWidth = round(aspectRatio * size.height)
    let aspectHeight = round(size.width / aspectRatio)

    if aspectWidth > size.width {
      return CGSize(width: size.width, height: aspectHeight)
    } else {
      return CGSize(width: aspectWidth, height: size.height)
    }
  }

  /// Finds a new size filling the given size while keeping the aspect ratio.
  ///
  /// - parameter size: The contraining size.
  /// - returns: size A new size that fills the contraining size keeping the same aspect ratio.
  func filling(_ size: CGSize) -> CGSize {
    let aspectWidth = round(aspectRatio * size.height)
    let aspectHeight = round(size.width / aspectRatio)

    if aspectWidth > size.width {
      return CGSize(width: aspectWidth, height: size.height)
    } else {
      return CGSize(width: size.width, height: aspectHeight)
    }
  }
}