osx橡皮擦刷背景

Question

我使用CGBlendModClear来绘制位于背景视图顶部的平滑视图。

let rep = viewToCapture.bitmapImageRepForCachingDisplayInRect(viewToCapture.bounds)!
viewToCapture.cacheDisplayInRect(viewToCapture.bounds, toBitmapImageRep: rep)        
let img = LmImage(size: viewToCapture.bounds.size)
img.addRepresentation(rep)

橡皮擦的区域是黑色

Answer 1

橡皮擦路径代码

    CGContextSetLineCap(context, CGLineCap.Round)
    CGContextSetBlendMode(context, .Clear)
    CGContextSetLineWidth(context, self.strokeWeight)
    CGContextStrokePath(context)

compositeView的快照 enter image description here

我想要的结果是 enter image description here