避免在特定的宽度和高度以下调整图像大小

Question

我想在服务器上上传图像时对其进行压缩。但是图像不应压缩到特定的高度和宽度以下。

下面是图像压缩的代码

func compressImage(image:UIImage) -> Data? {
    // Reducing file size to a 10th

    var actualHeight : CGFloat = image.size.height
    var actualWidth : CGFloat = image.size.width
    let maxHeight : CGFloat = 640.0
    let maxWidth : CGFloat = 640.0
    var imgRatio : CGFloat = actualWidth/actualHeight
    let maxRatio : CGFloat = maxWidth/maxHeight
    var compressionQuality : CGFloat = 1.0

    if (actualHeight > maxHeight || actualWidth > maxWidth){
        if(imgRatio < maxRatio){
            //adjust width according to maxHeight
            imgRatio = maxHeight / actualHeight
            actualWidth = imgRatio * actualWidth
            actualHeight = maxHeight
        }
        else if(imgRatio > maxRatio){
            //adjust height according to maxWidth
            imgRatio = maxWidth / actualWidth
            actualHeight = imgRatio * actualHeight
            actualWidth = maxWidth
        }
        else{
            actualHeight = maxHeight
            actualWidth = maxWidth
            compressionQuality = 1
        }
    }

    let rect = CGRect(x: 0.0, y: 0.0, width: actualWidth, height: actualHeight)
    UIGraphicsBeginImageContext(rect.size)
    image.draw(in: rect)
    guard let img = UIGraphicsGetImageFromCurrentImageContext() else {
        return nil
    }
    UIGraphicsEndImageContext()
    guard let imageData = img.jpegData(compressionQuality: compressionQuality)else{
        return nil
    }
    return imageData
}

但是我不希望图像的宽度和高度小于250。如何避免这种情况？