Objective-Cで書かれた画像（NSImage）を回転させるコードをSwiftに移植してみました。
オリジナル
rotate a NSImage · GitHub
https://gist.github.com/Rm1210/10621763
Swiftのコード
extension NSImage {
// 角度は反時計回り指定
func rotatedImage(degrees: CGFloat) -> NSImage {
let deg = fmod(degrees, 360)
if deg == 0 {
return self
}
let orgSize = self.size
var maxSize = NSSize()
switch deg {
case 90, 270, -90, -270:
maxSize = NSMakeSize(orgSize.height, orgSize.width)
case 180, -180:
maxSize = orgSize
default:
maxSize = NSMakeSize(20+max(orgSize.width, orgSize.height), 20+max(orgSize.width, orgSize.height))
}
let rot = NSAffineTransform()
rot.rotate(byDegrees: degrees)
let center = NSAffineTransform()
center.translateX(by: maxSize.width / 2, yBy: maxSize.height / 2)
rot.append(center as AffineTransform)
let rotatedImage = NSImage(size: maxSize)
rotatedImage.lockFocus()
rot.concat()
let rect = NSMakeRect(0, 0, orgSize.width, orgSize.height)
let corner = NSMakePoint(-orgSize.width / 2, -orgSize.height / 2)
draw(at: corner, from: rect, operation: .copy, fraction: 1.0)
rotatedImage.unlockFocus()
return rotatedImage
}
}