UIImageDeviceSpecific.swift

import UIKit

public enum DeviceSpecific {
	case iPhone
	case iPhoneRetina
	case iPhone5
	case iPhone6
	case iPhone6Plus
	case iPad
	case iPadRetina
	case Unknown
}

public extension UIImage {

	private class func currentDeviceSpecific() -> DeviceSpecific {
		
		let h = Float(UIScreen.mainScreen().bounds.size.height)
		let w = Float(UIScreen.mainScreen().bounds.size.width)
		let pixelDimension = Int(fmaxf(h, w))
		
		switch pixelDimension {
		case 480:
			return UIScreen.mainScreen().scale > 1.0 ? .iPhoneRetina : .iPhone
		case 568:
			return .iPhone5
		case 667:
			return .iPhone6
		case 736:
			return .iPhone6Plus
		case 1024:
			return UIScreen.mainScreen().scale > 1.0 ? .iPadRetina : .iPad
		default:
			return .Unknown
		}
	}
	
	private class func suffixForDevice() -> String {
		switch currentDeviceSpecific() {
			case .iPhone:
				return ""
			case .iPhoneRetina:
				return "@2x"
			case .iPhone5:
				return "-568h@2x"
			case .iPhone6:
				return "-667h@2x"
			case .iPhone6Plus:
				return "-736h@3x"
			case .iPad:
				return "~ipad"
			case .iPadRetina:
				return "~ipad@2x"
			case .Unknown:
				return ""
		}
	}
	
	public class func imageForSpecificDevice(imageName: String) -> UIImage? {
		var result: UIImage? = nil
		let nameWithSuffix = imageName.stringByAppendingString(UIImage.suffixForDevice())
		result = UIImage(named: nameWithSuffix)
		if result == nil {
			result = UIImage(named: imageName)
		}
		return result
	}
}