Generate an NSImage containing a checkerboard pattern for a specific size.

NSImage+checkerboard.swift

private extension NSImage {
   static func checkerboardImage(ofSize: CGSize, color1: NSColor, color2: NSColor, checkSize: CGFloat = 8) -> NSImage? {
      let width = NSNumber(value: Float(checkSize))
      let center = CIVector(cgPoint: CGPoint(x: 0, y: 0))
      let darkColor = CIColor(cgColor: color1.cgColor)
      let lightColor = CIColor(cgColor: color2.cgColor)
      let sharpness = NSNumber(value: 1.0)

      guard let filter = CIFilter(name: "CICheckerboardGenerator") else {
         return nil
      }

      filter.setDefaults()
      filter.setValue(width, forKey: "inputWidth")
      filter.setValue(center, forKey: "inputCenter")
      filter.setValue(darkColor, forKey: "inputColor0")
      filter.setValue(lightColor, forKey: "inputColor1")
      filter.setValue(sharpness, forKey: "inputSharpness")

      let context = CIContext(options: nil)
      guard let cgImage = context.createCGImage(filter.outputImage!, from: CGRect(origin: .zero, size: ofSize)) else {
         return nil
      }
      return NSImage(cgImage: cgImage, size: ofSize)
   }
}