Convert image to grayscale

ImageToGrayscale.swift

func convertImageToGrayScale(image: UIImage) -> UIImage {
    // Create image rectangle with current image width/height
    let imageRect: CGRect = CGRectMake(0, 0, image.size.width, image.size.height)
    
    // Grayscale color space
    let colorSpace: CGColorSpaceRef = CGColorSpaceCreateDeviceGray()
    
    // Create bitmap content with current image size and grayscale colorspace
    let bitmapInfo = CGBitmapInfo(CGImageAlphaInfo.None.rawValue)
    var context = CGBitmapContextCreate(nil, UInt(image.size.width), UInt(image.size.height), 8, 0, colorSpace, bitmapInfo)
    
    // Draw image into current context, with specified rectangle using previously defined context (with grayscale colorspace)
    CGContextDrawImage(context, imageRect, image.CGImage)
    
    // Create bitmap image info from pixel data in current context
    let imageRef: CGImageRef = CGBitmapContextCreateImage(context)
    
    // Create a new UIImage object
    let newImage: UIImage = UIImage(CGImage: imageRef)!
    
    // Return the new grayscale image
    return newImage
}