如何在Swift 3中为图像添加不透明度的黑色

Question

我想知道如何在Swift 3中的图像顶部放置一个不透明的黑色矩形。例如：

Answer 1

您可以使用不透明度创建一个黑色的UIView ，并使其与UIImageView大小相同，并将其添加为子视图。 尝试类似的东西：

let tintView = UIView()
tintView.backgroundColor = UIColor(white: 0, alpha: 0.5) //change to your liking
tintView.frame = CGRect(x: 0, y: 0, width: imageView.frame.width, height: imageView.frame.height)

imageView.addSubview(tintView)

imageView =你的UIImageView

Answer 2

func drawRectOn(image: UIImage) -> UIImage {
    UIGraphicsBeginImageContext(image.size)
    image.draw(at: CGPoint.zero)
    let context = UIGraphicsGetCurrentContext()

    // set fill gray and alpha
    context!.setFillColor(gray: 0, alpha: 0.5)
    context!.move(to: CGPoint(x: 0, y: 0))
    context!.fill(CGRect(x: 0, y: 0, width: image.size.width, height: image.size.height))
    context!.strokePath()
    let resultImage = UIGraphicsGetImageFromCurrentImageContext()

    // end the graphics context
    UIGraphicsEndImageContext()

    return resultImage!

}