如何在运行时以编程方式创建多分辨率（Retina-ready）NSImage？

I have two button images, say "myButton.png" and "[email protected]" in my app's bundle resources. At run time, I load the image using [NSImage imageNamed:@"myButton"] and need to split it into three slices and create three NSImages to use in NSDrawThreePartImage() function.I have two button images, say "myButton.png" an