CGBitmapContext

bitmapcontext.swift

// Here we provide the structure of our bitmap context

struct BitmapContextConfig {
    var bitsPerComponent: Int
    var bytesPerPixel: Int
    var space: CGColorSpace
    var bitmapInfo: CGBitmapInfo
    var data: UnsafeMutablePointer<Void> = nil
}

// A default gray context

let grayContext: BitmapContextConfig = {
    let space = CGColorSpaceCreateWithName(kCGColorSpaceGenericGray)!
    let bitmapInfo = CGBitmapInfo()
    return BitmapContextConfig(bitsPerComponent: 8, bytesPerPixel: 8, space: space, bitmapInfo: bitmapInfo, data: nil)
}()

// A default RGB context

let rgbContext: BitmapContextConfig = {
    let space = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB)!
    let info = CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedLast.rawValue)
    
    return BitmapContextConfig(bitsPerComponent: 8, bytesPerPixel: 4, space: space, bitmapInfo: info, data: nil)
}()

// Creating a new context

func createContext(width: Int, height: Int, config: BitmapContextConfig) -> CGContext? {
    return CGBitmapContextCreate(config.data, width, height, config.bitsPerComponent, width*config.bytesPerPixel, config.space, config.bitmapInfo.rawValue)
}

createContext(800, height: 600, config: rgbContext)