OSX/Cocoa command line program to create a bitmap, draw into it and save as a PNG. In this case it draws triangles that are used a basic grass asset

grass.swift

import Cocoa

private func saveAsPNGWithName(fileName: String, bitMap: NSBitmapImageRep) -> Bool
{
	let props: [NSObject:AnyObject] = [:]
	let imageData = bitMap.representationUsingType(NSBitmapImageFileType.NSPNGFileType, properties: props)
	
	return imageData!.writeToFile(fileName, atomically: false)
}

private func drawGrassIntoBitmap(bitmap: NSBitmapImageRep)
{
	var ctx = NSGraphicsContext(bitmapImageRep: bitmap)
	
	NSGraphicsContext.setCurrentContext(ctx)
	
	NSColor(red: 124 / 255, green: 252 / 255, blue: 0, alpha: 1.0).set()
	
	let path = NSBezierPath()
	
	path.moveToPoint(NSPoint(x: 0, y: 0))
	
	for i in stride(from: 0, through: SIZE.width, by: 40)
	{
		path.lineToPoint(NSPoint(x: CGFloat(i + 20), y: CGFloat(arc4random_uniform(400))))
		path.lineToPoint(NSPoint(x: i + 40, y: 0))
	}
	
	path.stroke()
	path.fill()
}

let SIZE = CGSize(width: 800, height: 400)

if Process.arguments.count != 2
{
	println("usage: grass <file>")
	exit(1)
}

let grass = NSBitmapImageRep(bitmapDataPlanes: nil, pixelsWide: Int(SIZE.width), pixelsHigh: Int(SIZE.height), bitsPerSample: 8, samplesPerPixel: 4, hasAlpha: true, isPlanar: false, colorSpaceName: NSDeviceRGBColorSpace, bytesPerRow: 0, bitsPerPixel: 0)
	
drawGrassIntoBitmap(grass!)
saveAsPNGWithName(Process.arguments[1], grass!)