A Swift version of this SO answer: http://stackoverflow.com/questions/603907/uiimage-resize-then-crop#605385

scale-and-crop-image.swift

// credit: http://stackoverflow.com/questions/603907/uiimage-resize-then-crop#605385
func scaleAndCropImage(_ image:UIImage, toSize size: CGSize) -> UIImage {
    // Make sure the image isn't already sized.
    guard !image.size.equalTo(size) else {
        return image
    }

    let widthFactor = size.width / image.size.width
    let heightFactor = size.height / image.size.height
    var scaleFactor: CGFloat = 0.0

    scaleFactor = heightFactor

    if widthFactor > heightFactor {
        scaleFactor = widthFactor
    }

    var thumbnailOrigin = CGPoint.zero
    let scaledWidth  = image.size.width * scaleFactor
    let scaledHeight = image.size.height * scaleFactor

    if widthFactor > heightFactor {
        thumbnailOrigin.y = (size.height - scaledHeight) / 2.0
    }

    else if widthFactor < heightFactor {
        thumbnailOrigin.x = (size.width - scaledWidth) / 2.0
    }

    var thumbnailRect = CGRect.zero
    thumbnailRect.origin = thumbnailOrigin
    thumbnailRect.size.width  = scaledWidth
    thumbnailRect.size.height = scaledHeight

    // Why use `UIGraphicsBeginImageContextWithOptions` over `UIGraphicsBeginImageContext`?
    // see: http://stackoverflow.com/questions/4334233/how-to-capture-uiview-to-uiimage-without-loss-of-quality-on-retina-display#4334902
    UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
    image.draw(in: thumbnailRect)
    let scaledImage = UIGraphicsGetImageFromCurrentImageContext()!
    UIGraphicsEndImageContext()

    return scaledImage
}

Thanks man! it solved my big problem!