UIImageResize.swift

extension UIImage {
  func resized(toWidth width: CGFloat) -> UIImage? {
    let canvasSize = CGSize(width: width, height: CGFloat(ceil(width/size.width * size.height)))
    UIGraphicsBeginImageContextWithOptions(canvasSize, false, scale)
    defer { UIGraphicsEndImageContext() }
    draw(in: CGRect(origin: .zero, size: canvasSize))
    return UIGraphicsGetImageFromCurrentImageContext()
  }
  func resizedImageWith(targetSize: CGSize) -> UIImage {
    let imageSize = self.size
    let newWidth  = targetSize.width  / self.size.width
    let newHeight = targetSize.height / self.size.height
    var newSize: CGSize
    if(newWidth > newHeight) {
      newSize = CGSize(width: imageSize.width * newHeight, height: imageSize.height * newHeight)
    } else {
      newSize = CGSize(width: imageSize.width * newWidth,  height: imageSize.height * newWidth)
    }
    let rect = CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height)
    UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0)
    self.draw(in: rect)
    let newImage = UIGraphicsGetImageFromCurrentImageContext()!
    UIGraphicsEndImageContext()
    return newImage
  }
}