Sample of drawing into a bitmap

myplayground.swift

import Cocoa

print( NSImageRep.registeredClasses ) // -> [NSPDFImageRep, NSPICTImageRep, NSEPSImageRep, NSBitmapImageRep]

func test() {
	guard let rep = NSBitmapImageRep(bitmapDataPlanes: nil,
									 pixelsWide: 256,
									 pixelsHigh: 256,
									 bitsPerSample: 8,
									 samplesPerPixel: 4,
									 hasAlpha: true,
									 isPlanar: false,
									 colorSpaceName: .deviceRGB,
									 bitmapFormat: .alphaFirst,
									 bytesPerRow: 0,	// auto
									 bitsPerPixel: 32) else {
		print("Failed to make graphics context")
		return
	}
	
	NSGraphicsContext.saveGraphicsState()
	NSGraphicsContext.current = NSGraphicsContext(bitmapImageRep: rep)
	
	// Draw content...
	
	let r = NSRect(x: 10.0, y: 10.0, width: 30.0, height: 30.0)
	let path = NSBezierPath(rect: r)
	NSColor.red.set()
	path.fill()
	NSGraphicsContext.restoreGraphicsState()
	
	guard let data = rep.representation(using: .png, properties: [:]) else {
		print("Failed to make png data representation")
		return
	}
	
	var url = FileManager.default.homeDirectoryForCurrentUser
		.appendingPathComponent("Desktop/examplepng.png", isDirectory: false)
		.standardizedFileURL
		.path
	print(url)
	if !FileManager.default.createFile(atPath: url,
									   contents: data,
									   attributes: [:]) {
		print("create file failed")
	} else {
		print("PNG created at: \(url)")
	}
}

test()