Extensions for converting NSImage <-> CGImage <-> CIImage

ImageConversion.swift

extension NSImage {
   /// Create a CIImage using the best representation available
   ///
   /// - Returns: Converted image, or nil
   func asCIImage() -> CIImage? {
      if let cgImage = self.asCGImage() {
         return CIImage(cgImage: cgImage)
      }
      return nil
   }

   /// Create a CGImage using the best representation of the image available in the NSImage for the image size
   ///
   /// - Returns: Converted image, or nil
   func asCGImage() -> CGImage? {
      var rect = NSRect(origin: CGPoint(x: 0, y: 0), size: self.size)
      return self.cgImage(forProposedRect: &rect, context: NSGraphicsContext.current, hints: nil)
	}
}

extension CIImage {
   /// Create a CGImage version of this image
   ///
   /// - Returns: Converted image, or nil
   func asCGImage(context: CIContext? = nil) -> CGImage? {
      let ctx = context ?? CIContext(options: nil)
      return ctx.createCGImage(self, from: self.extent)
   }

   /// Create an NSImage version of this image
   /// - Parameters:
   ///   - pixelSize: The number of pixels in the result image. For a retina image (for example), pixelSize is double repSize
   ///   - repSize: The number of points in the result image
   /// - Returns: Converted image, or nil
   #if os(macOS)
   @available(macOS 10, *)
   func asNSImage(pixelsSize: CGSize? = nil, repSize: CGSize? = nil) -> NSImage? {
      let rep = NSCIImageRep(ciImage: self)
      if let ps = pixelsSize {
         rep.pixelsWide = Int(ps.width)
         rep.pixelsHigh = Int(ps.height)
      }
      if let rs = repSize {
         rep.size = rs
      }
      let updateImage = NSImage(size: rep.size)
      updateImage.addRepresentation(rep)
      return updateImage
   }
   #endif
}

extension CGImage {
   /// Create a CIImage version of this image
   ///
   /// - Returns: Converted image, or nil
   func asCIImage() -> CIImage {
      return CIImage(cgImage: self)
   }

   /// Create an NSImage version of this image
   ///
   /// - Returns: Converted image, or nil
   func asNSImage() -> NSImage? {
      return NSImage(cgImage: self, size: .zero)
   }
}

Noice!