func maskImage(image: UIImage, mask: UIImage) -> UIImage {
    let imageReference = image.cgImage!
    let maskReference = mask.cgImage!
    
    let width = maskReference.width
    let height = maskReference.height
    let bitsPerComponent = maskReference.bitsPerComponent
    let bitsPerPixel = maskReference.bitsPerPixel
    let bytesPerRow = maskReference.bytesPerRow
    
    let context = CGContext(
        data: nil,
        width: width,
        height: height,
        bitsPerComponent: bitsPerComponent,
        bytesPerRow: bytesPerRow,
        space: CGColorSpaceCreateDeviceGray(),
        bitmapInfo: CGImageAlphaInfo.none.rawValue
    )
    
    context!.draw(maskReference, in: CGRect(x: 0, y: 0, width: width, height: height))
    
    let maskImage = context!.makeImage()!
    
    let maskedReference = imageReference.masking(maskImage)!
    
    return UIImage(cgImage: maskedReference)
}

这段代码专门为蒙版图像创建了一个新的CGContext，并将颜色空间设置为灰度（CGColorSpaceCreateDeviceGray()），以确保只有黑色像素被视为不透明。CGImageAlphaInfo.none参数用于指定遮罩图像没有Alpha通道。
通过将maskReference绘制到context中，创建了具有保留所有非黑色像素的期望行为的遮罩。然后，使用maskImage来掩蔽imageReference，从而产生具有所需效果的图像。