cannot invoke * with an argument list of type ($T12,@lvalue CGFloat)

阅读错误答案：

mainView.frame.size.width的类型为CGFloat,因此需要将CGFloat转换为Float

尝试将值设置为CGFloat或cast Float(image.size.width)

在操场上

选项1

let image = UIImage(named:"group_1.png") // just for example

let value:CGFloat = 10.0

let width:Float   = Float(image.size.width / 100.0 * value)

选项2

let value:Float = 10.0
let width:Float   = Float(image.size.width) / 100.0 * value