NSImage extension that allows initializing an image from a Base64 encoded string.

NSImage+Base64.swift

import AppKit

extension NSImage {

    convenience init?(base64EncodedString: String) {
        guard
            let url = URL(string: base64EncodedString),
            let data = try? Data(contentsOf: url)
        else {
            return nil
        }

        self.init(data: data)
    }
}