我需要使用 NSSlider 控制我上传的图像(JPEG、PNG、TIFF 等)的透明度(或不透明度)。我该怎么做?这是用 AppDelegate.swift 编写的代码
@IBAction func importButton(sender: AnyObject) {
let uploadFile: NSOpenPanel = NSOpenPanel()
uploadFile.allowsMultipleSelection = false
uploadFile.canChooseFiles = true
uploadFile.canChooseDirectories = false
uploadFile.runModal()
let chosenPicture = uploadFile.URL
if(chosenPicture != nil) {
let pictureImport = NSImage(contentsOfURL: chosenPicture!)
imageWell.image = pictureImport
}
}
@IBAction func brightnessSlider(sender: AnyObject) {
//var alpha = sender...
}