ios - UIImage 屏蔽不起作用(Swift，iOS 10)

Question

尝试使用我的自定义 mask 来遮盖图像。我想我关注the ideas正确，但由于某种原因，图像没有被遮盖。相反，由于未应用蒙版，蒙版后创建的蒙版图像包含原始裁剪图像。

这是 Swift playground 代码，可以用来测试我的代码(附有图像和蒙版，只需将它们放到资源文件夹中):

import UIKit

extension UIImage {
    static func resizeImage(image: UIImage, width: CGFloat) -> UIImage {
        let scale = width / image.size.width
        let newHeight = round(image.size.height * scale)
        UIGraphicsBeginImageContextWithOptions(CGSize(width:width, height:newHeight), false, image.scale)

        image.draw(in: CGRect(origin: CGPoint(x:0, y:0), size: CGSize(width: width, height: newHeight)))
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return newImage!
    }

    static func resizeImage(image: UIImage, height: CGFloat) -> UIImage {
        let scale = height / image.size.height
        let newWidth = round(image.size.width * scale)
        UIGraphicsBeginImageContextWithOptions(CGSize(width:newWidth, height:height), false, image.scale)
        image.draw(in: CGRect(origin: CGPoint(x:0, y:0), size: CGSize(width: newWidth, height: height)))
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return newImage!
    }
}

let image = UIImage(named: "image.jpg")!
var mask = UIImage(named: "mask.jpg")!

let k1 = image.size.width / image.size.height
let k2 = mask.size.width / mask.size.height

if k1 >= k2
{
    mask = UIImage.resizeImage(image: mask, height: image.size.height)
}
else
{
    mask = UIImage.resizeImage(image: mask, width: image.size.width)
}

image
mask

let center = CGPoint(x: image.size.width/2, y: image.size.height/2)
let croppingRect = CGRect(x: abs(image.size.width-mask.size.width)/2*image.scale,
                                  y: abs(image.size.height-mask.size.height)/2*image.scale,
                                  width: mask.size.width*image.scale,
                                  height: mask.size.height*image.scale).integral
let maskReference = mask.cgImage!
let imageReference = image.cgImage!.cropping(to: croppingRect)!
let imageMask = CGImage(maskWidth: maskReference.width,
                        height: maskReference.height,
                        bitsPerComponent: maskReference.bitsPerComponent,
                        bitsPerPixel: maskReference.bitsPerPixel,
                        bytesPerRow: maskReference.bytesPerRow,
                        provider: maskReference.dataProvider!, decode: nil, shouldInterpolate: true)

imageMask?.colorSpace
imageMask?.alphaInfo

let maskedReference = imageReference.masking(imageMask!)
let maskedImage = UIImage(cgImage:maskedReference!, scale: image.scale, orientation: image.imageOrientation)

Answer 1

swift 4+

let icon = UIImageView(image: YOURIMAGE)
icon.frame = CGRect(x:100, y: 100, width: 100, height: 100)
icon.layer.masksToBounds = true
let maskView = UIImageView()
maskView.image = YOURMASKIMAGE
maskView.frame = icon.bounds
icon.mask = maskView
icon.contentMode = .scaleToFill
icon.clipsToBounds = true
view.addSubview(icon)