Draws Image in a target size. If it's aspect ratio won't fit in the size, it's cropped.

NSImageExtensions.swift

extension NSImage {
    func drawInTargetSize(targetSize: NSSize) -> NSImage? {
        let aspectRatio = max(targetSize.width/self.size.width, targetSize.height/self.size.height)
        let newSize = NSSize(width: self.size.height * aspectRatio, height: self.size.height * aspectRatio)
        var newRect = NSRect(origin: NSPoint(x: 0, y: 0), size: newSize)
        
        let ctx = NSGraphicsContext()
        guard let resizedImage = self.CGImageForProposedRect(&newRect, context: ctx, hints: nil) else { return nil }
        
        let yOffset = (newSize.height > targetSize.height) ? floor((newSize.height - targetSize.height)/2.0) : 0
        let xOffset = (newSize.width > targetSize.width) ? floor((newSize.width - targetSize.width)/2.0) : 0
        
        guard let croppedImage = CGImageCreateWithImageInRect(resizedImage, CGRect(x: xOffset, y: yOffset, width: targetSize.width, height: targetSize.height)) else { return nil }
        
        return NSImage(CGImage: croppedImage, size: targetSize)
    }
}