render-icon-playground.swift

//: Playground - noun: a place where people can play

import Cocoa

enum ImageError: Error {
    case couldNotCreateBitmapImage
    case couldNotCreatePNGRepresentation
}

func renderIcon(text: String, backgroundColor: NSColor, sizeInPixels: Int) throws -> Data {
    guard let imageRep = NSBitmapImageRep(bitmapDataPlanes: nil, pixelsWide: sizeInPixels, pixelsHigh: sizeInPixels, bitsPerSample: 8, samplesPerPixel: 4, hasAlpha: true, isPlanar: false, colorSpaceName: .calibratedRGB, bytesPerRow: 0, bitsPerPixel: 0) else {
        throw ImageError.couldNotCreateBitmapImage
    }
    NSGraphicsContext.current = NSGraphicsContext(bitmapImageRep: imageRep)
    
    let string = text as NSString
    
    let width = CGFloat(sizeInPixels)
    let imageSize = NSSize(width: width, height: width)
    let font = NSFont.systemFont(ofSize: width * 0.843)
    let attributes: [NSAttributedString.Key : Any] = [.font: font]
    
    let rect = string.boundingRect(with: imageSize, options: [], attributes: attributes)
    
    NSColor.white.setFill()
    NSRect(x: 0, y: 0, width: width, height: width).fill()
    string.draw(in: NSRect(x: width / 2 - rect.width / 2,
                           y: width / 2 - rect.size.height / 2 ,
                           width: rect.width,
                           height: rect.height),
                withAttributes: attributes)

    guard let data = imageRep.representation(using: .png, properties: [:]) else {
        throw ImageError.couldNotCreatePNGRepresentation
    }
    return data
}

let imageData = try renderIcon(text: "🍓", backgroundColor: .white, sizeInPixels: 100)
let url = URL(fileURLWithPath: "/Users/simon/Desktop/Icon100.png")
try imageData.write(to: url)