Getting average color in NSImage using Swift (extension) - Used in https://github.com/musa11971/Music-Bar/

NSImage+Music-Bar.swift

//
//  NSImage+Music-Bar.swift
//  Music Bar
//
//  Created by Musa Semou on 13/12/2019.
//  Copyright © 2019 Musa Semou. All rights reserved.
//

import AppKit

extension NSImage {
	/// Returns the average color that is present in the image.
	var averageColor: NSColor? {
		// Image is not valid, so we cannot get the average color
		if !isValid {
			return nil
		}
		
		// Create a CGImage from the NSImage
		var imageRect = CGRect(x: 0, y: 0, width: self.size.width, height: self.size.height)
		let cgImageRef = self.cgImage(forProposedRect: &imageRect, context: nil, hints: nil)
		
		// Create vector and apply filter
		let inputImage = CIImage(cgImage: cgImageRef!)
		let extentVector = CIVector(x: inputImage.extent.origin.x, y: inputImage.extent.origin.y, z: inputImage.extent.size.width, w: inputImage.extent.size.height)

		let filter = CIFilter(name: "CIAreaAverage", parameters: [kCIInputImageKey: inputImage, kCIInputExtentKey: extentVector])
		let outputImage = filter!.outputImage!

		var bitmap = [UInt8](repeating: 0, count: 4)
		let context = CIContext(options: [.workingColorSpace: kCFNull!])
		context.render(outputImage, toBitmap: &bitmap, rowBytes: 4, bounds: CGRect(x: 0, y: 0, width: 1, height: 1), format: .RGBA8, colorSpace: nil)

		return NSColor(red: CGFloat(bitmap[0]) / 255, green: CGFloat(bitmap[1]) / 255, blue: CGFloat(bitmap[2]) / 255, alpha: CGFloat(bitmap[3]) / 255)
	}
}

For those without ultra-ultra-ultra wide monitors:

extension NSImage {
    
    var averageColor: NSColor? {
        
        // Image is not valid, so we cannot get the average color
        if !isValid { return nil }
        
        // Create a CGImage from the NSImage
        var imageRect = CGRect(
            x: 0,
            y: 0,
            width: self.size.width,
            height: self.size.height
        )
        let cgImageRef = self.cgImage(
            forProposedRect: &imageRect,
            context: nil,
            hints: nil
        )
        
        // Create vector and apply filter
        let inputImage = CIImage(cgImage: cgImageRef!)
        let extentVector = CIVector(
            x: inputImage.extent.origin.x,
            y: inputImage.extent.origin.y,
            z: inputImage.extent.size.width,
            w: inputImage.extent.size.height
        )
        
        let filter = CIFilter(
            name: "CIAreaAverage",
            parameters: [
                kCIInputImageKey: inputImage,
                kCIInputExtentKey: extentVector
            ]
        )
        let outputImage = filter!.outputImage!
        
        var bitmap = [UInt8](repeating: 0, count: 4)
        let context = CIContext(options: [.workingColorSpace: kCFNull!])
        context.render(
            outputImage,
            toBitmap: &bitmap,
            rowBytes: 4,
            bounds: CGRect(x: 0, y: 0, width: 1, height: 1),
            format: .RGBA8,
            colorSpace: nil
        )
        
        return NSColor(
            red: CGFloat(bitmap[0]) / 255,
            green: CGFloat(bitmap[1]) / 255,
            blue: CGFloat(bitmap[2]) / 255,
            alpha: CGFloat(bitmap[3]) / 255
        )
        
    }
}