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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...
}
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1 回答 1

1

尝试这个

@IBAction func brightnessSlider(sender: NSSlider) {

    var alpha = sender.minValue + (sender.doubleValue-sender.minValue)/(sender.maxValue-sender.minValue)
    imageWell.alphaValue = CGFloat(alpha)


}

minValue如果您始终为 0 ,则 alpha 的计算会变得更简单:

var alpha = sender.doubleValue/sender.maxValue
于 2016-08-03T21:56:25.193 回答