Generate CGColors to match UIColors

CGColorGenerator.swift

//: Known-Good: Version 9.0 beta 5 (9M202q)

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



import UIKit


//: This playground is for generating code to define CGColors to match UIColors

/**
 Parse UIColor.description and generate Swift code for a CGColor
 */
fileprivate func parseUIColorDescription( line:String) -> String
{
  let tokens = line.components(separatedBy: CharacterSet(charactersIn: " "))
  let colorspaceString = tokens.first!
  let valueTokens = tokens.dropFirst()

  switch colorspaceString {
  case "UIExtendedSRGBColorSpace":
    let rgba = valueTokens.map({
      (s) -> CGFloat in
      CGFloat(Float(s)!)
    })

    let code:String = "CGColor.fromRGB(rgba:\(rgba))\n"
    return code

  case "UIExtendedGrayColorSpace":
    let grayA = valueTokens.map({
      (s) -> CGFloat in
      CGFloat(Float(s)!)
    })
    let code:String = "CGColor.fromDevice(graya:\(grayA))\n"
    return code

  default:
    fatalError("unexpected")
  }

  return line
}

/// Generate code to define a CGColor based on a UIColor
fileprivate func generateCGColorDefinition(_ c:UIColor) -> String {
  let s = c.description
  return parseUIColorDescription(line: s)
}

/// Generate code defining static CGColor constants matching the UIColor constants

func generateCGColorExtensionDefinitionForUIColors() -> String
{
  let colorNames:[UIColor:String] = [.black: "black",
                                     .blue: "blue",
                                     .brown: "brown",
                                     .clear: "clear",
                                     .cyan: "cyan",
                                     .darkGray: "darkGray",
                                     .gray: "gray",
                                     .green: "green",
                                     .lightGray: "lightGray",
                                     .magenta: "magenta",
                                     .orange: "orange",
                                     .purple: "purple",
                                     .red: "red",
                                     .white: "white",
                                     .yellow: "yellow"]

  var lines:[String] = []
  for (color,colorName) in colorNames {
    let cgColorDefinition:String = generateCGColorDefinition(color)
    let line = "static var \(colorName):CGColor {\n return \(cgColorDefinition) }"
    lines.append(line)
  }

  return "extension CGColor {\n" + lines.joined(separator: "\n") + " \n } "
}

//let s = generateCGColorExtensionDefinitionForUIColors()
//print(s)

/// Extension needed to use generated CGColor definitions
extension CGColor
{
  static func fromRGB(rgba array:[CGFloat]) -> CGColor {
    let colorSpace = CGColorSpaceCreateDeviceRGB()
    return array.withUnsafeBufferPointer({ (ptr) -> CGColor in
      let baseAddress = ptr.baseAddress!
      let color = CGColor(colorSpace: colorSpace, components: baseAddress)!
      return color
    })
  }

  static func fromDevice(graya array:[CGFloat]) -> CGColor {
    let colorSpace = CGColorSpaceCreateDeviceGray()
    return array.withUnsafeBufferPointer({ (ptr) -> CGColor in
      let baseAddress = ptr.baseAddress!
      let color = CGColor(colorSpace: colorSpace, components: baseAddress)!
      return color
    })
  }
}

// generated:

extension CGColor {
  static var magenta:CGColor {
    return CGColor.fromRGB(rgba:[1.0, 0.0, 1.0, 1.0])
  }
  static var orange:CGColor {
    return CGColor.fromRGB(rgba:[1.0, 0.5, 0.0, 1.0])
  }
  static var red:CGColor {
    return CGColor.fromRGB(rgba:[1.0, 0.0, 0.0, 1.0])
  }
  static var yellow:CGColor {
    return CGColor.fromRGB(rgba:[1.0, 1.0, 0.0, 1.0])
  }
  static var lightGray:CGColor {
    return CGColor.fromDevice(graya:[0.666666984558105, 1.0])
  }
  static var black:CGColor {
    return CGColor.fromDevice(graya:[0.0, 1.0])
  }
  static var purple:CGColor {
    return CGColor.fromRGB(rgba:[0.5, 0.0, 0.5, 1.0])
  }
  static var green:CGColor {
    return CGColor.fromRGB(rgba:[0.0, 1.0, 0.0, 1.0])
  }
  static var clear:CGColor {
    return CGColor.fromDevice(graya:[0.0, 0.0])
  }
  static var cyan:CGColor {
    return CGColor.fromRGB(rgba:[0.0, 1.0, 1.0, 1.0])
  }
  static var darkGray:CGColor {
    return CGColor.fromDevice(graya:[0.333332985639572, 1.0])
  }
  static var brown:CGColor {
    return CGColor.fromRGB(rgba:[0.600000023841858, 0.400000005960464, 0.200000002980232, 1.0])
  }
  static var blue:CGColor {
    return CGColor.fromRGB(rgba:[0.0, 0.0, 1.0, 1.0])
  }
  static var white:CGColor {
    return CGColor.fromDevice(graya:[1.0, 1.0])
  }
  static var gray:CGColor {
    return CGColor.fromDevice(graya:[0.5, 1.0])
  }
}