[英]Programmatically Set UIImage Animation with WatchKit in Swift
[英]How to set the alpha of an UIImage in SWIFT programmatically?
我在這里找到了很多解決方案,但不適用於Swift ,我知道您可以使用 UIImageView 來做到這一點,但在我的情況下,我需要以編程方式為UIButton設置 alpha 透明背景圖像。 最好是 UIImage 擴展!
let img = UIImage(named: "imageWithoutAlpha")
var imgInsets = UIEdgeInsetsMake(0, 24, 0, 24)
image = image!.resizableImageWithCapInsets(imgInsets)
let myButton = UIButton(frame: CGRect(x: 50, y: 50, width: img!.size.width, height: img!.size.height))
myButton.setBackgroundImage(img, forState: UIControlState.Normal)
myButton.contentEdgeInsets = UIEdgeInsetsMake(0, 20, 0, 20)
myButton.setTitle("Startbutton", forState: UIControlState.Normal)
myButton.setTitleColor(UIColor.blackColor(), forState: UIControlState.Normal)
myButton.sizeToFit()
view.addSubview(myButton)
當前結果:
想要的結果:
幸運的是,我能夠幫助自己,並想與您分享我的解決方案:
斯威夫特 3
// UIImage+Alpha.swift
extension UIImage {
func alpha(_ value:CGFloat) -> UIImage {
UIGraphicsBeginImageContextWithOptions(size, false, scale)
draw(at: CGPoint.zero, blendMode: .normal, alpha: value)
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage!
}
}
我將上述新的 Swift 擴展添加到我的項目中,然后我更改了 UIButton 示例,如下所示,以獲得透明度為 50% 的 alpha 透明背景圖像。
let img = UIImage(named: "imageWithoutAlpha")!.alpha(0.5)
let myButton = UIButton()
myButton.setBackgroundImage(img, for: .normal)
最簡單的方法是將UIImage
放在UIImageView
並在那里設置 alpha。
let image = UIImage(named: "imageWithoutAlpha")
let imageView = UIImageView(image: image)
imageView.alpha = 0.5
myButton.setBackgroundImage(image, forState: UIControlState.Normal)
斯威夫特 5,iOS 10+
如果您的應用不支持 iOS 10 之前的操作系統,那么您可以利用更強大的UIGraphicsImageRenderer
UIKit 繪圖 API。
extension UIImage {
func withAlpha(_ a: CGFloat) -> UIImage {
return UIGraphicsImageRenderer(size: size, format: imageRendererFormat).image { (_) in
draw(in: CGRect(origin: .zero, size: size), blendMode: .normal, alpha: a)
}
}
}
用法
let img = UIImage(named: "someImage")?.withAlpha(0.5)
我能夠使用以下代碼設置 alpha:
self.imageView.image = UIImageView(image: "image.png")
imageView.alpha = 0.5
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