How do set a width and height of an Image in Swift

My suggestion is.

Instead of set size of image you should set size of UIImageView and then put this image on it so, size of image will be display as per your requirement.

Such like,

var imageView = UIImageView(frame: CGRectMake(100, 150, 150, 150)); // set as you want
var image = UIImage(named: "myImage.png");
imageView.image = image;
self.view.addSubview(imageView);