Swift 4 String extension for converting an emoji to an NSImage. Idea and original code by Daniel Jalkut http://indiestack.com/2017/06/evergreen-images/.

emojiImage.swift

import Cocoa

extension String {
    
    // https://stackoverflow.com/a/36258684/2227743
    var containsEmoji: Bool {
        for scalar in self.unicodeScalars {
            switch scalar.value {
            case 0x1F600...0x1F64F, // Emoticons
            0x1F300...0x1F5FF, // Misc Symbols and Pictographs
            0x1F680...0x1F6FF, // Transport and Map
            0x2600...0x26FF,   // Misc symbols
            0x2700...0x27BF,   // Dingbats
            0xFE00...0xFE0F,   // Variation Selectors
            0x1F900...0x1F9FF:  // Supplemental Symbols and Pictographs
                return true
            default:
                continue
            }
        }
        return false
    }
    
    // Idea and original code by Daniel Jalkut http://indiestack.com/2017/06/evergreen-images/
    // Converted to a Swift 4 String extension by https://github.com/ericdke
    func emojiImage(width: Int = 1024, height: Int = 1024) -> NSImage? {
        guard width > 24,
            !self.isEmpty,
            self.containsEmoji,
            let drawingContext = CGContext(data: nil, width: width, height: height,
                                           bitsPerComponent: 8, bytesPerRow: 0,
                                           space: CGColorSpaceCreateDeviceRGB(),
                                           bitmapInfo: CGImageAlphaInfo.premultipliedFirst.rawValue)
        else {
            return nil
        }
        let imageSize = NSSize(width: width, height: height)
        let targetRect = NSRect(origin: .zero, size: imageSize)
        let font = NSFont.systemFont(ofSize: CGFloat(width - 24))
        NSGraphicsContext.saveGraphicsState()
        NSGraphicsContext.current = NSGraphicsContext(cgContext: drawingContext, flipped: false)
        NSString(string: String(self.first!)).draw(in: targetRect, withAttributes: [.font: font])
        NSGraphicsContext.restoreGraphicsState()
        if let coreImage = drawingContext.makeImage() {
            return NSImage(cgImage: coreImage, size: imageSize)
        }
        return nil
    }
    
}