Swift Playground for creating an icon.

IconPlayground.playground

//: A Cocoa based Playground to present user interface

import AppKit
import PlaygroundSupport

let nibFile = NSNib.Name("MyView")
var topLevelObjects : NSArray?

Bundle.main.loadNibNamed(nibFile, owner:nil, topLevelObjects: &topLevelObjects)
let views = (topLevelObjects as! Array<Any>).filter { $0 is NSView }


func main() -> NSImage? {
    let color = NSColor.clear
    
    let size = CGFloat(128)
    let view = NSView(frame: NSRect(x: 0, y: 0, width: size, height: size))
    view.wantsLayer = true
    view.translatesAutoresizingMaskIntoConstraints = false
    view.layer?.backgroundColor = color.cgColor
    view.layer?.cornerRadius = 2
    
    let destinationSize = Double(size)
    
    let image = NSImage(size: NSSize(width: destinationSize, height: destinationSize))
    
    guard let icon = NSImage(systemSymbolName: "lightbulb.fill", accessibilityDescription: nil) else { return nil }
    guard let frameIcon = NSImage(systemSymbolName: "lightbulb", accessibilityDescription: nil) else { return nil }
    
    var width = Double(1)
    var height = Double(1)
    
    print(icon.size)
    
    if icon.size.width < icon.size.height {
        width = destinationSize * (icon.size.width / icon.size.height)
        height = destinationSize
    } else {
        width = destinationSize
        height = destinationSize * (icon.size.height / icon.size.width)
    }
    
    let x = (destinationSize - width) / 2
    let y = (destinationSize - height) / 2
    
    image.lockFocus()
    guard let ctx = NSGraphicsContext.current?.cgContext else { return nil }
    
    view.layer?.render(in: ctx)
    let source = NSRect(origin: CGPoint.zero, size: icon.size)
    
    let destination = NSRect(x: x, y: y, width: width, height: height)
    
    
    ctx.setFillColor(NSColor.blue.cgColor)
    let rect = CGRect(x: x+1, y: y, width: width-2, height: height)
    rect.fill()
    
    icon.draw(in: destination, from: source, operation: .destinationIn, fraction: 1)
    frameIcon.draw(in: destination, from: source, operation: .darken, fraction: 1)
    image.unlockFocus()
    
    return image
}

if let image = main() {
    let imageview = NSImageView(image: image)
    
    // Present the view in Playground
    PlaygroundPage.current.liveView = imageview
}