问在Swift、Cocoa、Mac中旋转NSImage

EN

extension NSImage {
    /// Rotates the image by the specified degrees around the center.
    /// Note that if the angle is not a multiple of 90°, parts of the rotated image may be drawn outside the image bounds.
    func rotated(by angle: CGFloat) -> NSImage {
        let img = NSImage(size: self.size, flipped: false, drawingHandler: { (rect) -> Bool in
            let (width, height) = (rect.size.width, rect.size.height)
            let transform = NSAffineTransform()
            transform.translateX(by: width / 2, yBy: height / 2)
            transform.rotate(byDegrees: angle)
            transform.translateX(by: -width / 2, yBy: -height / 2)
            transform.concat()
            self.draw(in: rect)
            return true
        })
        img.isTemplate = self.isTemplate // preserve the underlying image's template setting
        return img
    }
}